there you go, all been said above
I take the fact that such an obvious measure of public mood isn't incorporated into the voting slips is tacit acknowledgement by the powers that be that they know it wouldn't look good for them. It would also undermine the coming tax rise so we can directly fund their grubby little clubs. At present, if all parties want us to fund them, and we vote one of them in, we voted to directly give them a cut of our earnings via whatever tax they choose to levy. You will not be allowed to opt out of funding political parties as 'the people' will have voted for it by voting for any of them.
To be fair, it's a great business if you can get into it. You can't really blame people for spotting a soft route to money and influence.