I have nothing but a basic grasp of economics so my thinking could easily be way off, but if you're giving Joe the Barista in your local Costa a pay rise of 10%, that's probably not going to put him far off his direct supervisors hourly rate, so keep the supervisor happy you're going to give them a bump too. Then the store manager is going to want a bump, and before you know it pay his risen a fair way up the chain. That increased money in peoples pockets mean that the market might be able to bear (bare?) higher prices, which means prices go up and the people at the lower end of the wage spectrum are still not much better off in real terms.
Having said that, anything we can do to encourage people back to work, and not turning down work because it would make them worse off, is a step in the right direction.