I have worried about this incentive too, but they've just yesterday released some software that moves in this direction (though characterizing it as a special case for people who need extra security). But in the past I feared that they would even periodically update Gmail in ways that would break compatibility with browser-based encryption; I think the fact that they're publishing their own end-to-end browser-based e-mail encryption software shows that they're at a minimum willing to accept it as a supported feature.