In addition to the jobs and contractor issue, there's also the fact that there was still some Cold War pressure to keep up with the Soviets.

That factor was much reduced by the 1970s compared to the near panic of the post-Sputnik era -- that level of panic was teh only reason a program as expensive as Apollo ever got funded in the first place.

Even if it was clear the SOviets weren't overtaking us on a cosmic race to somewhere, it was clear that they weren't abandoning space, and by the early 70s were working towards space stations. Would would manned space stations do to give the Soviets a military advantage? That's not so obvious, and was even less obvious for us, since we could build more capable unmanned satellites than them. But no one wanted to take the risk that they were getting something out of it, and so we should too.

More generally, even if you had good arguments that the Soviets weren't getting anything out of a manned program that was worth the cost, there are plenty of politicians who would have raised a stink about "abandoning the high ground of space to the communists!". So long as the Russians acted is if putting humans in orbit was important, we couldn't afford to walk away from it politically.

So, even if you weren't going to spend the money to go to Mars, you had to do _something_, and that's another factor in mix of how we ended up with our directionless program.