Switch hitting...specifically Berkman

[fifield]

I assume the reason hitters develop this ability is to better their productivity by creating more favorable angles on pitches. But if it doesn't work, why switch hit?
Lance Berkman's career numbers clearly show switch hitting doesn't work for him. No way he'd match that futility against left handed pitching as a left handed batter.
I didn't notice it before this season, and I didn't notice it for the first half of this season, but for the past six weeks I've been benching him against left handed pitching, and though he's had a couple good games where I've kicked myself, it's clear he sucks as a right handed hitter.
So why the [censored] does he continue to hit right handed?

Edit to add non-rhetorical question: Does Berkman hitting so poorly right handed diminish or actually improve his fantasy value? Meaning, if it's clear exactly when a player will suck and when he won't, does that make up for the lost playing time during the periods he sucks?