You don't "have" to do anything. But the competitors that have been out competing for a year or more have run these tyres and set times on these tyres. Like most others, I'm not too bothered about trophies but I am bothered about knowing I'm improving and beating my own times, so why would I want to turn up to a venue and go 3 seconds slower, when I have a perfectly serviceable set of super soft tyres sat in the garage that could make me quicker?
Don't go me wrong, I agree with your sentiment and it has a place in the future, but not to be implemented in an overnight ruling that eliminates a tyre without any consultation. You're making the point that you don't want to spend £500 on tyres - well I did spend £500 on tyres, just 8 months ago, so why should it be ok to make that worthless overnight? Fine if we're given due warning and it's set for 2017 maybe, then I won't reinvest in another set at the end of next year and move to whatever 1a or 1b tyre is suitable. But we weren't given due warning, and rightly so me and 76 (so far) other competitors say we'd rather be consulted and use the tyres we've got for at least another season.