Perhaps they don't want the MS type people. They generally cost Amex a lot in frequent sign up bonuses but don't provide long term revenue.
They want long term consistent spenders, and if you need MS to reach a 3k sign up bonus they probably wont make much on you long term.
I think you're understanding the value of "MS type people" to the banks. We're excellent marketers for their products.
In discussing various forms of travel hacking/MS schtick, several friends/family members have decided to apply for all sorts of CC's. They're drawn in by hearing about all the free stuff I've gotten but due to lack of time/patience never end up maxing out the valuable benefits for themselves.
I'm sure we all know friends/relatives who have CSR/Amex plats but don't even get around to redeeming the travel credits. Maybe they maintain one or more ink cards but hardly spend anything on 5x categories.
It kills me inside but I have friends who pay interest charges/late fees on CC's that I "convinced" them to get.