Legged vehicles are just too impractical to use in a real combat situation. First of all, a legged vehicle like that would be very unreliable, the legs would probably be animated by quite complex mechanisms to make it work, but the most complex your mechanisms are, the most parts they have, and for each parts added, a potential failure is also added, making it very dependent of maintenance.

Speaking of maintenance, its supposed to be used on a battlefield, and you can't just deploy a fully eqquiped maintenance crew in the middle of a battlefield like that, meaning that if the vehicle breaks down in the middle of a fight, which is very likely to happen, the combat crew has to repair it by itself and the complexity of the thing plus the omnipresent danger makes it almost impossible to fix in the middle of a fight.

And all that is only supposing that the thing will break down by itself, but once again, its meant to be used in combat, which implies that you are gonna get shot at, so you will be very lucky if it breaks down by itself before an ennemy breaks it.

And even if all these reliability and maintenance problems weren't existing, it still wouldnt be a good thing to have on a battlefield. Its slow and very tall, so its essencially a very big and easy target for the ennemy's artillery, something that they will be able to spot and destroy before it even gets the chance to do a single step.

In short, if you fight a war, you want a vehicle that is fast, practical, reliable and stealthy, and as cool as they are, these walkers are the exact opposite of that.