What is the utility of an inhouse DevOps if cloud providers already provide professional services?
Some good reasons could be:

The salary of an inhouse devops is pretty sure less expensive as the consultants.
The consultants are only assigned during a limited period, to temporary add (wo)manpower, e.g. while putting together the infrastructure.
The consultants come with specific expertise that the inhouse devops do not (yet) have, whereas part of the job of the consultants is to perform knowledge transfer and/or on the job training for the inhouse devops.
The consultants are there to do the boring parts of the work, whereas the inhouse devops are assigned to the strategic / long term tasks (so that when the consultants leave, the know how doesn’t leave the company also.

BTW, IMO the best consultants are those who:

Say their jobdescription is like “My job is to make sure that you don’t need me anymore ...”.
Never touch the keyboard, and instead always coach / help inhouse devops to have them complete any task (it seems so easy when you see somebody else complete some task, but it is way more difficult to complete it yourself).