If they could find even simple life forms on Mars and see how they were different/similar to life on Earth, that might provide some clues as to how life came about.
Also, the more places they find life, the more likely there is life throughout the Universe.
Until they started seeing planets around other suns, we could only surmise how many planets there might be in the universe. Now we have a pretty good idea. Maybe we won't be visiting them soon, but it is something that is nice to know and keeps the scientists busy doing things other than screaming about global climate change.
And even that doesn’t get ET to first base. The whole world had to evolve if it was going to lead its inhabitants to evolve. Speaking hypothetically.
Well I understand your points but I’m not sure the best use of our money is to spend billions on a Mission to Mars whose primary purpose is to determine if Mars once harbored bacteria or even now does. I would rather spend it prospecting for minerals. We know those are there. Of course even if we find gold in large quantities that would not make it worthwhile to bring it back to earth but we could build infrastructure on Mars with what we find. It costs hundreds of billions to put raw materials in space so if you have some that are already in space why not just st leave them there? Actually I think it makes more sense to do it on the moon than on Mars.