I have some products which I am putting out into the world. In the past I've worked freelance for others. I am aware of my skillset, and it has mainly focussed on the making side of the development of products. I need to focus on promotion, events, connecting with my community which I have been developing along the way. What are the benefits of bringing others with specialised skills in to help out?
I'm probably at risk of stating the obvious here but...
...because they'll have specialized skills to help out with?
In the end it all comes down to what you can afford. If you have the budget for it, you'll be best off hiring highly specialized people for each individual type of task within your business. It stands to reason that those specialized people would be the best at performing that particular task (both in terms of efficiency and effectiveness).
If you don't have money then it's a case of trying to do as much of it as possible yourself (at the compromise of quality) and outsourcing the highest 'return on investment' work to domain experts.
I hope my answer made some sense for your vague question.