Entry denied because you come too often – whats the deal?

Hi everybody,
With some confusion Im reading more and more comments and see more and more threads coming up from people that do enter Thailand several times per year on Visa Exemption (= allowed to stay up to 30 days for most countries) mentioning that…
– they got refused to enter and sent back
or
– got any stamps/comments/marks under their stamp that their next entry will most likely be dienied because you come too often without proper visa
or
– are questioned in a private room and let in 1 last time being told next time they have to come with a proper visa.
I dont know what exactly the deal is or if Im just a super lucky guy but in my passport I have over 20 (!) pages with stamps from Suvarnabhumi airport officers showing my record of the past 5-6 years: I never ever had or applied for a Visa, I always present my passport at immigration at Suvarnabhumi airport and get a stamp (Visa Exemption) that allows me to stay up to 30 days. I never ever was questioned about my strange looking passport with tons of stamps and even more the huge entry list the computer must show the officer that checks/scans my passport. I come to Thailand by plane 7-9 times every year and stay between 12-20 days per trip. Never longer (maybe one time 2 or 3 years ago I did stay 25 days) because I need to take care of my business in Europe as well and that for cant afford to stay 4+ weeks.
Just wondering if anyone got an idea why I never faced any issues why other members here do have so many problems while having far less stamps/entries than me over the past months/years?