Why has infection of .exe files fallen out of favor with virus writers?

Question

Malware

When I first started working with computers, viruses that infect executable files were very common. Now I can safely insert a flash drive into a computer infected with modern malware and the hash sums of all my files will remain unchanged. (I check before starting)
Why did viruses use autorun instead of infecting .exe and replacing folders with shortcuts?

Answer 1

Apparently the answer is obvious.

Answer 2

this is practically the only "semi-legal" method of infection that virus writers have left and which is relatively rarely detected by antiviruses.