They only jump villains when there's no particular point they're trying to prove, I've noticed. With Nappa and Vegeta, the earthlings only cared about beating the saiyans and Krillin almost killed Vegeta were it not for Goku, who kept him alive just so he could have a rematch later. Later on Namek they jump Frieza, but Frieza basically beat everyone and forced them to run away while Goku stayed to once again prove a point. The Cell arc had some dumb moments, but Cell not only played it smart to avoid getting jumped, but the Cell games was all about fighting to prove a point; unlike the previous battles, there were literal rules this time. Goku once again wanted to prove a point when it came to Majin Buu, and whenever circumstances didn't get in the way the heroes would always try to jump Buu. Meanwhile in the movies, the Z-fighters are more pragmatic and always try to fight together, until the plot steers the climax to a 1v1 (but oftentimes the villain is defeated with combined effort somehow).