A lot of rather (surprisingly) big-name movie folks did commercials in the 1950s/60s. Ditto for magazine ads in the 30s/40s/50s. There was not considered any shame or unseemliness about doing so. If anything, there was a certain pride, taking on and representing a product. It wasn’t until the later crop of late-60s/70s/80s modern-era baby-boomer stars that seemed to have an inflated attitude of themselves, and that they were apparently too good for such things, and would be ‘lowering’ themselves to be involved in such ‘commercial’ work!
JK Simmons is a guy who gets big roles but has no problem doing those insurance ads as the instructor.