Obviously this depends on social circles and family traditions, as some groups only give cash gifts and others do not for any occasion.
In my experience not online, I have yet to personally meet anyone in family, friends or acquaintances who give cash gifts because it’s not done, even from parents to kids. Fiancé comes from similar social circles where only physical gifts are given for both showers and weddings. The “cover your plate” concept is not a consideration as well because you don’t charging guests to attend unless you are a business. There is no way they could begin to estimate what is spent not is it their business as they did not contract the vendors or arrange the payments. The only time anyone we know has mentioned not getting registry gifts is that the items were too expensive for the guests to afford.
Most people can use upgrades and extras of what they already own if they truly don’t want anything. Say you want a new frappe machine that you saw at Target that cuts down on your daily Starbucks bill. Why not put that on the registry? If you host holidays at your home, chances are you have a second or third bedroom that needs sheets and blankets. If you host game night or bbqs, get something related to that if the traditional housewares are not your thing. If there is no physical registry guests will purchase items that you don’t want and can’t return anywhere. It’s how they celebrate with you. Cash is not the default in many social circles and families. With a registry, you pick out specific items you need and want in a wide range of prices because everyone has their own budget. Also several wedding vendors on Instagram have mentioned specifically to view it as “a wish list of stuff you want but would never spend your own money on”. That makes it easier for guests.
In the real world outside of WW/Pinterest/Instagram etc, what is your experience?