You need a change agent. Sometimes will be the Scrum Master, sometimes not.

For me the big mistake is consider teams as something fixed forever. A Scrum Master is very helpful for the first stages of a team. Once you achieve the high-performance teams, maybe this role could be avoided. The team is mature enough. We are speaking about months, even years....

When we speak about "dedicated" SM sometimes we consider 1 squad for 1 Scrum Master. I've never seen this in real life. We handle several teams, with several deep organizational changes and we are not in the "ideal scenario" as a company. Normally we need to think before in how is our organization in terms of agile structure and then we will have an answer to this.