I don't know what the parent's reasoning is, but the problem I have with "let's just tax it!" is that there's probably already taxes being taken from that money

I don't know what the parent's reasoning is, but the problem I have with "let's just tax it!" is that there's probably already taxes being taken from that money somewhere along the line. The next response is usually "well that's fine" - no, it isn't always - or "well we'll stop some or all of those others," which doesn't necessarily happen. Finally, while a tax may ostensibly exist to pay for x, there's usually nothing stopping existing funding y from being reappropriated for z once the new tax is in place. So there can be a new tax to increase funding but there's no net gain. I don't have any sources but I firmly believe that this happens. So, short answer: because politics.