Airlines have never been particularly interested in 250 hour "self improvers". Never!
Why is that? The answer is simple, it is because 250 hour CPL "self improvers" never existed until the advent of JAA licence harmonisation.
There were always a small number of 250 hour cadet pilots that were recruited in to the handful of airlines with cadet programmes, but they were almost always from "approved" integrated training schools that by and large followed the same format as todays evolved "approved schools," those being the major players in supplying full time integrated graduates to those airlines with cadet programmes. Yesterdays Hamble (an in house BOAC/BEA/BA college) and Oxford, Perth etc. evolved into todays Oxford, FTE and CTC.
The old self improver route meant acquiring at least 700 hours (outside of one of these integrated "approved" programmes,) for the issue of a CPL/IR. Even then, that level of experience was unlikely to find an invitation to interview letter landing on your doormat. Most of the airlines looked for candidates with at least 2000 hours and for the jet operators usually around 500 hours of turbine experience. The successful "self improvers" often amassed this through a variety of "stepping stone" jobs, such as flight instruction (which could be remunerated in those days with a PPL!), Air taxi, Aerial work, Third and Second tier turboprop operators, etc. In that respect the airlines requirements have generally changed little.
The reduction in experience levels to 250 hours was done to bring the UK and a few other countries into line with other ICAO signatory nations and other supranational authorities. Indeed the UK became a signatory to one such supranational authority (the then JAA now EASA), and hence the need for change. Previous sources of remunerated employment such as flight instruction were now subject to a CPL requirement, and hence the experience level for the issue of the CPL was reduced to 250 hours to bring the requirements into line with those existing in the USA and most of the rest of the world.
The rapid expansion of at least one lo-co airline in Europe also coincided broadly with these changes. That airline sought co-pilot applications within the strict letter of the law to anybody with a CPL/IR and the necessary application fee. This seemed to generate a popular perception (that persists to this day) that 250 hours and a CPL/IR was the golden ticket to the right seat of jet airliner. Unfortunately it wasn't! It never had been, and the fact that the new requirements slashed the basic flying hour requirements by two thirds, only served to open the floodgates to what was nearly always an overflowing reservoir.
This relative explosion of new hopefuls clutching a CPL/IR, and the general industry wide reduction of turboprop opportunities, as well as an increasing lack of general aviation openings, resulted in the situation you see now. When you then add on the global economic cycles, the changes in industry requirements, and the deluge of swimmers looking for any employment rock to cling on to, the normal progression avenues for the self improver simply became hopelessly constricted.
Those schools that evolved from the old "approved" schools expanded their cadet programmes in association with more and more airlines. Those airlines that continued to seek "experienced" (military and civil pilots) throughout a prolonged economic downturn continued to expect experience levels at pretty much the same benchmark that they had always done.
The one sector of the marketplace that was squeezed out was the new and vastly expanded low hour "self improver." The first tier airlines always (albeit in smaller numbers) took their cadets from the big Three "approved schools." They also recruited experienced civil pilots from the "stepping stone" operators, and they took experienced ex-military career changers.
Over the last 10-15 years, coupled with a very long and severe economic recession, there also occurred global regulatory changes that raised pilots retirement ages from 55 to 60 and then 65. This took pressure off airlines for an entire decade as they experienced far fewer retirements than they normally might, and allowed them to expand their cadet programmes to take up the shortfall. The result of this was an evolution of the industrial landscape, such that now the cadet programmes have also served to squeeze a good deal of the middle ground "experienced pilot" recruitment. That squeeze manifested itself as far less opportunity, and vastly reduced T&C's (in many cases) for those same experienced career movers.
The industry has seismically shifted over the last 20 years from a highly regulated and restricted one, to one where "low cost" is the name of the game. The secret is in the name. Low cost means low input costs wherever you can control those costs, right through to low prices for the end consumer. The writing has been on the wall for quite a long time now. You can explain the real time history on here until you are blue in the face, but for those adversely affected, or those who failed to appreciate the general realities, or continue to stick their head in the sand or their fingers in their ears, it simply won't make a jot of difference. To succeed in an evolving environment, it is usually necessary to evolve with it. That is more difficult when you have already rolled the dice!