Unlike Google Reader, this product was replaced with a newer (and, IMO, better) alternative, Google Photos. Albums you had in Picasa aren't gone, they're just accessible through the new UI. Why should Google maintain two competing UIs for the same product?

[these opinions are my own, not necessarily those of my employer, Google]

I used Picasa to organize my photos offline, so Photos is in no way a replacement. Are there any plans to open source the desktop application?

Google Reader should have been though. If they have used that as the core of Google+ then it could have had a shot at becoming the next Facebook.

And what's their core part? Self-driving cars?

I would put it this way. Google Photos blows away Picasa Web Albums and Imgur is a better host. It was dead as Flickr will be in the next year or so sadly.

I understand that, but they broke the web by killing it.

Advertising. If it doesn't relate to advertising or have some ad revenue channel, don't expect it to stick around for long.

... but it could be. They still can serve ads there!

I was being sarcastic...