Having the team feel direct pain is a great motivator for building robust applications - if you know that that quick hack could lead to you getting paged at 3 in the morning you are far more likely to seek out additional solutions(anecdotally speaking) - it means you also have weight within the team to make the right engineering calls.
The team can bond over operations - it sucks being oncall, everyone knows that so everyone tries to make it less sucky, by clearing ops queues before handing off or making ticket messages a bit nicer.
When you start having ticket-free weeks or months it is an awesome feeling, the service works and is robust and your team can spend that time writing new stuff.
Additionally, when you have a small team building/maintaining a service it makes far more sense to rotate the oncall responsibility between them rather than an external engineer.