Never trust user input. The users already can't modify the server.

And what actual applications did you have in mind that warrant throwing everybody under the bus? (by that I mean some applications (allegedly) need it, so it gets forced on everyone)

The one that's so incredibly broken that Apple and Visa keep blaming eachother when they get a report that you can steal any amount by making yourself pass as a transit card ? Cool security theater. https://hackernoon.com/veritasium-stole-$10000-from-mkbhds-l...