Divided evenly across citizens and given lump-sum, the bulk of the money would be likely spent within the next few months, creating a spike of economic activity. People go shopping, businesses make some extra profit, maybe hire a new employee...

Maybe because using such taxes in a smart way is a smarter way of giving the money back?

What defines ‘smart’? I can think & consider & carefully plan — and still do something foolish. Moreover, what you consider wise I may consider foolish. Who am I to judge your choice, and who are you to judge mine?

It would certainly be democratic to give the money back to the citizens, permitting each to spend it as he will; then each would get a vote on what he thinks the best expenditure is.