It's such a busy station for being a local station (out of the TfL station types, the least-used), and the District Line beyond this is often quite crowded at rush hour -- it's rare that I get a seat starting from Turnham Green at rush hour.

Having the Piccadilly stopping here during the day would allow for better passenger distribution -- I've often found that one or the other line is brimming with passengers even when the other is half-empty.