Question about ranked AoS!?

Ive played over 600 matches trying to get to dawn spear. I made it to like 1283 but decided to keep playing for all that money you can make. Lol dropped to 850ish and climbed back up to 1217 finally. Heres my question. I noticed on the ranked boards there are ppl sitting at higher ranks and have played less than 20 matches… why doesn’t the game force you to play like 10 matches a week to maintain your spot? Or rather if you dont play you start to drop in rank by like 20 points every week or something…