I remember getting a boarding pass from an airline that was only offered in their app or printed at the airport, no email/download image/PDF option. I didn't have to install their app, but I would have had to waste time at the airport otherwise. I removed it when I was done and left it a negative review.
Should be. I bought tickets on the official website but they would not accept receipt or even verification from that website. Needed a qr code and only way to get it was with app. Had to step out of line, download the app, remember login I had generated from website, login and pull up the qr codes for my tickets.
In many cases this means avoiding the service altogether. So long as you are good with that, then yeah by all means, don't download it or use the service. I don't use plenty of services because I don't want their app. Instagram is one of those.