We had cash gifts given by guests since it was easy to put towards a goal or future plans. Its not a bad thing since most couples may be living together now and don't feel they want things keeping on the side unwanted. A nice phrase that has been used in Indian Invitations is No Boxed Gifts Please and your guests will respect your wish.
My husband and I made a registry and it had what we actually would have wanted (22 items total). Most people just sent cash in their cards anyway. We felt weird having a registry at all since it was a covid wedding and no one could actually BE there other then watch the Facebook live. But we actually received quite a few gifts off of it (which were great!) But most opted to do a card with money. I think it depends on the person giving the gift. 🙂
If you don't have a registry, most likely your guests will bring a monetary gift at the reception. If you want to make sure that your guests don't bring an actual gift like appliances and such, just let them know with your invitation that you'd rather have a monetary gift instead of actual gifts.
Agreed with both statements above. With no registry though you run the risk of people picking whatever physical gift they like and gifting it - some people do not like giving cash. We had a small registry and on it (used MyRegistry) had a picture, right at the top, of a little card with a silly poem saying we'd love contributions to our honeymoon and who to do that through (our travel agent set up a no fee account at the agency). The majority of people chose to gift cash straight to us but I feel this put the hint out there that we prefer it.
Most guests who choose to give cash would rather bring it with them and give it inside an envelope or card. Online cash registries will either charge a service fee or take a cut off the total so it's not worth it for all parties.