Because the time savings and utility value of using it as a primary (or at least primary for you individually and on the go) device far outweigh the cost. E.g.

Because the time savings and utility value of using it as a primary (or at least primary for you individually and on the go) device far outweigh the cost. E.g., have one big computer for the house, but let household members’ “personal computer” be an iPad Pro. Or, have one big workstation on your office desk, but let your roaming computer be an iPad Pro.