I believe the main reason is so you sub your account and pay money to CCCP.
Someone could say it is so newer players realized mining is the most boring. unfun and also least profitable thing to do. Which is all true except that is something CCCP don’t really want you to realize.
Seriously, do level 3 missions or combat sites/anomalies, or join a corp and salvage behind corp members or do ´data/relic in lowsec or wormholes. Anything is better than mining.
If you still want to do mining then please sub. train exhumers and mine in Hulk and later in untanked Orca with Harvester Drones. Also please buy and inject very expensive implants. Mine safe.