The choice? During that time, the server files weren't that popular nor fixed to a "usable" degree.
I remember the time where ecSRO, eSRO, PlaySRO, ZCZS SRO, etc. were online at once. Not these bunch of "corrupted, 1-day-fly, wanna be, die trying getting money on each player"-hosted crap servers.
The point "why they don't join all to 2-3 servers" - because of money, dude.
Everything goes and flows with money. Joining a pserver, without getting a cut of the income? Forget it - I MA GONNA OPEN MA KRYLL SARVUR AND MADE MONEY FAST! ME DEVELOPERZ BEST! - and that is the hole story about people advertising their server for 3 months, "STARTS ON 01/01/20XX JOIN!" and are up to 1-2 months only, until they get wrecked due to lack of package controlling, connection managing, "distributed denial of service attack"-protection, exploits on their agents and gateways and SMCs and Websites, and whatever being left.
It is just about money. Stolen server files (free) - goooood, spending some money for protection and saving the server-uptime for a long run - noooooooo.