Well I am a Scottish tax payer but I don't get a say in the matter either. However, there really is no justification for persisting with the Prestwick funding as there is clearly no realistic strategy to bring it back towards anything approaching self-sufficiency. For me it would be very useful as a fully functional airport in terms of ease of use and distance from my house (I live roughly half way between PIK and GLA) but the reality is that it is a massive financial drain and a waste of public money at this stage.
However, I think there is a lot of political will to see the airport remain open, which seems to go all the way to the top, so I expect the current setup to continue for the foreseeable future.