Well, not that they ever were, really, but TeleCheck has made them even less so. My story is similar to many others: lost my debit card, was left with only checks until the new card showed up, bank was out-of-state so no way to withdraw cash.
I wrote a check at Stop 'n' Shop and asked for cash back, it worked, tried again a couple of days later, blocked by TeleCheck but then they let it through for the exact amount. Tried at Wal-Mart shortly thereafter, denied, then denied again even for the exact amount. Got a couple of different explanations from them including lack of account history and spending patterns.
The upshot is that, due to TeleCheck and companies like them, checks are no longer a reliable way to access your funds.
I used to do the cash-back thing at grocery stores all the time as a teenager in the '90s, and all my checks were perfectly good.
(Even the pizza delivery guys at my college would accept checks!) I guess times have changed and checks are now a thing of the past. Debit cards, credit cards, and cash only!