so why aren't pictures of a roundearth able to be used as evidence for a round earth
Ostensibly, pizaaplanet took those photos himself (or was at the very least present when they were taken). If you take a photo of the earth that shows it to be a sphere yourself, feel free to show it to us, and it will have greater credibility than something you found on Google images claiming to be a photo of the earth from space. It's still just a photo, though, and we don't know for sure if it is what you purport it to be, just as you can't be sure PP isn't standing on a soundstage made to look like the Spirit of Tasmania II.