The USA covers a vast geographical area, and their public transport system on the ground isn't able to carry people between cities - airlines *are* the domestic public transport system. In the USA, the airlines function almost as a utility to the masses and almost as a way of keeping the country together. The likes of American, Delta, United, SouthWest, Alaska and JetBlue are strategically important to the USA
VS gave up flying domestic routes almost 5 years ago and show no sign of restarting them. Maybe if VS were flying a significant number of short-haul routes to mainland Europe, one could argue they were a public utility. If VS want public cash while struggling to make a profit (i.e. dubious that they will be able to repay the taxpayer loan), there needs to be a strategic benefit to the UK
A taxpayer subsidy for an airline that devotes a significant amount of its fleet to taking people to Disneyworld and Carribbean beaches, especially when demand for these destinations is likely to be lower than in the past (i.e. lower yield, lower load factor, lower revenues), is not a priority