It's a variety of factors. With the biggest one being leaders worried that burdening their own people would just get the entire thing canned. If you talk about cutting social programs or raising taxes, people are going to get pretty pissy real quick. Leaders want to give as much as they can, without having to entertain ideas like that. To not actually enter a war footing economically. Some countries have done more than others, Poland and the Baltics come to mind. They have known the horrors of Russia for a long, long time. And they have given quite a bit to keep those horrors as far away as possible.

There is, of course, the very real threat of nukes. Where if one doesn't boil the frog, the frog will lash out. Again, I think the pace is much too slow. Though, there is active talk of sending western troops to Ukraine and Trump has threatened to up the arms transfers and sanctions dramatically if Russia does not submit. It's looking like that might be exactly what happens as I don't see Putin backing down.

And to the point you directly bring up, there are absolutely people doing exactly that; people who want Russia to step on every caltrop possible instead of decisively forcing them to stop walking, thus inflicting less pain on Russia.

The reason is not singular, the reason is all of the above and many more.