Your point is valid. My devil's advocate on that scenario, however, would be that in basketball you can still meaningfully contribute offensively despite being a horrid free throw shooter. In baseball, pitchers normally are unable to contribute much at all offensively. You could argue that they should just work on being better batters, but would that take away from their time honing their craft of pitching? Not a question I can personally answer, but I'd rather have top-level pitching AND top-level batting than a lesser form of both.