I say this as someone who loves mecha-type robots and so on: They're not practical, not at the technology we have now. They're ponderous and clumsy, mechanically unreliable, difficult to armor, and have no advantages over wheeled and tracked vehicles - only disadvantages.
That might change in near future (look at some of the stuff Boston Dynamics is doing) but ... while that stuff makes me misty-eyed to see someone actually making fun stuff, it's not practical. It doesn't even live in the same city as "practical."