A couple things.
Again, both of those examples, Vegeta and Cell, had major pride in themselves and thought they were unbeatable. Because of that, especially in Cell's case, they may have would rather have been thoroughly thrashed instead of having to live with themselves having just barely deflected a beam from somebody they thought was way weaker than themselves.
That's just a theory of why they mightn't have done it in the show.
Another thing is that maybe they didn't even have the power to deflect the beam. They were probably in a fairly long fight already, and were all but completely spent. They may not have had the energy to even redirect the beam enough to save themselves. Either that, or their power levels didn't compare enough to have an effect quickly enough.
Anyways, those are just theories as to why it may not have happened on the show. Most, if not all, of the "bad guys" on the show had excessive pride in their own abilities. Frieza, for example, was pissed that he lost to "a monkey". So he continued attacking.
But in the game, if you don't have enough PL to compare, you can't PS in the first place. And if you don't have the ki to struggle, you can't even redirect the beam and will lose anyways. But if you have a comparable PL, you should at least be able to redirect it slightly, whether you have the ki to return it completely or not.
Someone is always winning the struggle. It is never won until the beams explode.
