Yeah... intelligent people are constantly trying to rationalise how "aviation" works, but unfortunately it doesn't work in an intelligent way
The system has been developed ad-hoc over many decades, to serve the airline business, and for most of that time it ran on a telex-based network (now called the AFTN, which presently runs on high speed telecom links, though I suspect some of it may use telex in parts of the deepest Africa
) which was used to send messages concerning flights, and lots of other stuff like issuing Notams, weather observations at airports (Metars), etc. In the 3rd world, some of the AFTN traffic even ran on short wave radio links, and there is/was quite a sizeable ham radio crowd which used to build kit to decode these transmissions
With telex, you did not need special integrity measures because the system always provided a receipt confirmation (as a result, telex messages carried almost total evidential weight in cases of a dispute). Good stuff.... I even remember my business telex number from 1978: 85715
Also the messages were always brief and standard and nobody needed to speak English to understand them. For example the flight plan (which is no more than just an AFTN message) is a standard layout.
Once the stuff went "electronic" and got disconnected at the human end (no more telex machine operators feeding in the paper tape) you didn't really know if anybody was reading it anymore.
VFR GA was never supported properly; most of the world doesn't know what it is...
Yes flight plans are legally required to cross national frontiers, so we have to file them.
I don't suppose anything is going to change anytime soon
The biggest change was over the past few years, when electronic (internet) filing arrived. Homebriefing.com was the first outfit and now there are numerous options. The UK agencies resisted this fiercely for as long as they could, because of likely job losses at the FBUs where dozens of people were sitting, filing about 3000 faxed VFR flight plans each month. Once the FBUs were closed, this job protection was no longer relevant and Afpex was introduced.
In Europe, the
IFR flight plan system runs on a centralised database (Eurocontrol, a.k.a. IFPS) and is a lot more robust. You file a flight plan, say 1hr before EOBT, and in seconds it pops up at the towers at both ends and as soon as your allocated transponder code is seen on radar (this detail varies according to country) the flight plan is sent to all IFR controllers along the filed route. The smoothness has to be seen to be believed. It does go wrong but rarely.