A non‑insignificant portion of them claim to be suitable for passport photos. Touching up a passport photo in any way (Photoshop or AI) is a brilliant way to get yourself denied a U.S. passport.
From the travel.state.gov [1] rules:
- Submit the original, unedited photo without filters or digital changes.
[1] - https://travel.state.gov/en/passports/apply/help/photos.html
I had a strange case for my passport renewal, where they were asking for an updated photo, and I got nicely dressed for my photo and the USPS clerk took it for me, but for some reason the Passport Office rejected it, on quite vague criteria. Then I resubmitted the whole thing verbatim, and it was accepted on the second go. I feel like they just wanted to add some friction to the process.