Handling Everything Yourself?
Thats fine if you have very little on your plate.
But if your workload is already swamped... this isn't a viable option.
New Staff?
Finding good people isn't easy, and training and onboarding staff is costly.
Then, if and once you do find the perfect candidate for the position...
You are still relying on one person!
Hire An Agency?
If you don't have a marketing budget of tens of thousands of dollars, you might end up having your account managed by the intern of the assistant's assistant. Which is also not exactly optimal.