Chewie drove an intact (practical) walker. BB-8 drove a (CGI) walker with only legs. Even if that should be possible (which I doubt), it looked bad. And then Rose and Finn hoped on, which also looked bad. Like something out of the PT.
Okay, if you’re talking execution I get it. I didn’t mind the shot where it reveals it’s BB-8, but it does look goofy when the whole crew hops on.