Its all about keeping things on the same stack. If you want to run a non-mission critical bot for your business… maybe it just gathers user stats or something like that… why does this need to be replicated 13 times?
It comes down to efficiency. Do the mission critical stuff on fully replicated subnets and do the hard data processing (non-mission critical) in the cheapest and fastest way.
HTTP outcalls currently go through consensus so they arent great for fast communication with the outside world. So any data procesing would be better inside the IC.
I give an example here -》 Data Processing Subnet