Don't develop for evil companies. I tried explaining this to my coworkers but they couldn't see beyond the $$$. Now I understand why Engineers take a 2 hour ethics class.
Spot on. SIWA is great for me because a whole class of apps I previously refused to use are now on the table.
It effectively forces apps to have an anonymized email login option, and even better, if said app starts abusing its access to my inbox, I can cut it off permanently even if the app offers no such option.