I wouldn't call a quick search for "fake text message" which returns dozens of generators significantly more effort. Harder to do on the spot, maybe, but the effort is negligible.
Cryptography sometimes seem to rely on a stronger version this too. With enough computing power, you can brute force a lot. Some authentication seems just expensive enough that only a nation-state actor would have enough resources to break it, and then rests on the assumption that the small subset of people who could put in enough effort won't care enough to do anything worth being concerned about.
This is also why, say, people lock their doors even if they have windows.