(That's what made me pay Google directly for the first time; extra storage for backing up photos.)
For the hobbyist or pro photographer backing up their full frame RAWs, sure, you want a more professional (read: paid) backup solution but that doesn't seem unfair to me. For the 95% of users who want to free up space taken up by vacation snaps and selfies, compressing photos over 16MP is often acceptable when it doesn't cost extra.
full picture https://images.huffingtonpost.com/2016-01-01-1451631423-7665...
cropped detail https://images.huffingtonpost.com/2016-01-01-1451631515-2060...
Also, I believe Photos storage is unlimited even in Original quality if you own a Pixel phone, which may or not may be the case, but still.
I'm wary of services that auto-compress images, because a) I want my bits to stay the way they were originally captured, and b) every now and then I have to print a photo I make, and then suddenly all those details matter for the print quality.