Timothy.
Your first sentence. Yes, ATCO's CAN be helpful and accommodating to GA especially - some might say, only - when their workload is light. If that is the case then that is understandable.
Aviation is divided into two broad strands: Commercial and GA. Commercial aviation pays the mortgage and the school fees, puts bread on the table and provides a dividend for shareholders.
It provides scientific research, new aircraft designs, complex airport terminals, managerial skills at all levels and a level of technical ability that permeates the entire global industry. What the accumulative value of all this is, I can only guess; many billions.
And GA ? Well, for most, it is a pleasant hobby. A desirable recreational pursuit. And really, that is it. We can pad it out a bit by referring to the FTO's it supports. All the instructors and the maintenance engineers, the chaps that sit on the gang mowers forever cutting grass in the summer etc.
The bald and unpalatable fact is that there is no real need for GA, anymore than there is for sailing small sailboats. It is a desirable hobby but not, in the scheme of things very essential.
I can hear 'Disgusted' of Tunbridge Wells muttering into his pint, who is this Kremmen fellow, just who does he think he is, rubbishing our beloved pastime. NO I AM NOT. I'm attempting a little balance, using a bit of perspective. Emphasising if you like the gulf that exists between the reality that is commercial aviation and that which is a pleasant, un-necessary but wholly delighful GA.
GA contributes nothing of any consequence to Commercial aviation and that is why GA is seen as an irrelevance.