1) Availability: Some places (like my hometown of 20,000 people) don't have ATMs.
2) Safety: Tellers are pretty much safe, ATMs are asking to be mugged.
3) Guarantee: If I deposit $100 cash in an ATM there is no guarantee the money will be deposited - a teller could pocket some or a theif could steal the ATM. I have no proof of the deposit and it is gone. I like to have a receipt showing the deposit made it into my account.
4) Cost: Tellers are free to use, ATMs come with pages of fees. Some charge a fee for any use no matter what (even your own bank). You might be charged for using a different banks ATM. Some charge for printing the receipt. Some charge a percent fee for withdraws. Etc. ATMs are money makers for banks, why am I going to fall into that trap?
5) Banks are everywhere - my banks are on the way to any store/restaurant/entertainment I've ever gone to. So an ATM isn't any more convenient than a bank branch. Plus at least with the ATMs on campus there is at least a dozen people in line for the ATM. It takes 20 minutes to get your money. I'd rather go to the bank right next door and get my money in 2-3 minutes.
6) You get next to no service at an ATM. What if you need a fee disputed, or a cashiers check, or loan, or new checks, or another debit card, etc?
So why should I pay fees for a less safe, unguaranteed transaction, that provides fewer services?
The day all ATM transactions are 100% free and they start charging to use the expensive tellers then I'll switch most of my business to an ATM.