In addition to what is mentioned by others, it starts the flow going to get a smooth pressure in the nozzle. While heating up the bed/nozzle, there can be an inconsistent melt in the nozzle. Sometimes a bit will ooze out and leave the nozzle empty. The purge will even all that stuff out and get fresh filament in there before it starts actually printing
I think there will be a market for “corporate compliant and secure!!” LLMs. “Pay us gobs of money so you don’t get ‘hacked’ by dumb LLM users”