I've been archiving all my email since 1999 using IMAP, with some POP3 in the middle there and now using a combination of both, depending on the mail account since I have about a dozen.

GMail blew out the barn doors (back in the day) for one reason only: 1GB of storage that continued to grow. As far as web-mail implementation, it was never and is still not the best available. It swelled in usage because Google required a GMail account for many other of its free services.

Picasa was a third-party application acquired by Google, the same as they did with Google Earth, Maps and Sketchup.

IMO, Sketchup and Picasa stagnated under Google ownership. Maps developed quite nicely as did Earth, but really it's just stuff that already existed, and continued to exist, elsewhere.