I'm still trying to figure out if people just didn't deposit cash somehow, or if they lined up to have human beings count and deposit cash for them??
Because I'm 99.9% positive that I learned about depositing cash in machines from a teller who rolled her eyes at me and said "you know you can just use the machine to deposit this, right?"
We lined up to have human beings count and deposit cash for us. At least my family did.
Many reasons for this back then, some of which still sometimes apply:
1. ATMs, when introduced, were mostly marketed as ways to get cash out of your account. The ability to deposit, check balances, and transfer money weren't emphasized and may not have been available until later.
2. Technically I think it's easier for ATMs to dispense cash than to collect it. For a (long?) while, you put your bills in an envelope, totaled it yourself, sealed the envelope, and then put it in the ATM, where later a teller would take the envelope, open it, double check the total, and then do the deposit for you. It was possible the teller would come up with a different total, and they'd adjust it for you on the deposit. Some people who knew how this worked (a) didn't see the envelope and ATM machine as helping much, and (b) didn't like the idea of their deposit being adjusted later.
3. Some tellers probably viewed ATMs as competition / automation taking their jobs, so they didn't see the incentive of telling customers they could use the ATMs instead of tellers.
4. ATMs never have, as far as I know, been able to take coins as deposit. Also, until recently, the ability to take checks as deposit was not available (at least not around here). Tellers can handle both coins and checks.
5. Some customers just like to deal with a person rather than a machine.
6. Similar to #4, one might have another banking matter to handle, such as asking about a car loan, or getting cash back in specific denominations like $2 bills for grandkids or tips, that an ATM may not handle. Might as well ask the question while the teller is handling a deposit.
7. It's just what we were used to. I still do some things "the old fashioned way" just because I'm comfortable doing them that way, even though there may be faster / easier ways of which I am aware. Because change takes effort and I might not have the spoons for it.