I finally figured out how the mempool and fees work and I've been watch the mempool constantly for a few days now. I have noticed lots people including ridiculously high fees. Like when 50 sat/vbyte is the minimum there were people including 6000 sat/vbyte. Or when 2 sat/vbyte would be enough like 30% of the people were setting there fees at 60 sat/vbyte.
1 or 2 satoshi/vbyte is only used if you are using a non-custodial wallet and be able to manually choose your fee. On exchanges or services, to avoid client complaints and avoid pressure on their customer support, they often choose overkilling fee for their clients. It is very easily to be seen with 1 or 2 MB from the tip of mempool. The total size of each fee level from 1-2 MB of mempool tip is usually very thin.
https://jochen-hoenicke.de/queue/#1,2h. The size of fee from 140 sat/vbyte to 170 sat/vbyte is 0.003 MB (0.067 MB to 0.097 MB).
People choose low fee are from non-custodial wallet users and they have good practice and know how bitcoin transaction, mempool and fee works.
Why do people set their fees so unnecessarily high? Is it simply because of how default fees are set in wallets, by exchanges, or by services? If so, why do professional developers miscalculate the fee so poorly?
Use exchanges, merchants, services and don't care to choose options (if available: normal, average, fast but not all services have those fee options). Companies get profits from it and many services have their static fee, not dynamic fee. Static fee means it is fixed and they can reset it manually but after each reset, fee will be fixed again.