Because I wouldn't want Google to know what links I click on. When I used to use Google, and they added such redirects that included the destination URL as a parameter, I'd edit the link to make it just that URL before resolving it. This new scheme would make that impossible.
I use a Firefox extension to rewrite those Google redirects into plain links, to remove Google tracking of which links I click. The extension is broken now
Blocking URL shorteners and google-ad links yes! Personally for me it's also the fact that this is effectively an unresolvable URL shortener, store that link somewhere and it will most likely be dead. Can't copy link anymore and paste it on a notepad or chat app to check it out later as there isn't a guarantee it will load at all (ie: the problem with url shorteners).
