I'm sure they would choose real factory building instead if it was just as easy (at least, I would) - no bureaucracy/planning conflicts, you are the sole dictator - full vertical integration, no supply costs or land costs - building is near-instant and perfectly reversible - machines don't have 6 month lead times or go out of stock - maintenance is done by magic, machines never break down - infinite research and information to build every machine from scratch
When I play Factorio with my friends, I don't have to sit through 1 hour planning meetings where half the people don't know what game we're playing and the other half want to make all decisions by committee in a future, unscheduled meeting.