I have a question. I'm wondering why big companies buy smaller companies but don't keep their branding. For instance, if Google bought Picaza, why not just make Picaza the de-facto image storage app? They'd replace their Photos app with Picaza, and call it a day. Something similar happened recently with Songza.

Is there any reason in particular why small companies are bought out by big companies and their brands are dissolved rather than building on top of their initial branding?