[Yodoshi]

Latency, Ops, Cost, specialised features like latency based routing (nearest datacentre to the user making a request).

It comes down to the same reasons as someone using the cloud or a cdn, why spend more running it yourself (staff, equipment etc) instead getting someone who's who job it is to run that specific piece of software to the absolute best of their ability.

It's just not a core competency of almost all companies.