I guess it's a generational thing. Going on a vacation where I have to pay for restaurants or tours with cash I'll bring hundreds of dollars. Going on a vacation like Disney where credit cards are generally accepted.. I'll still have a minimum of $20. Probably more. Too me "no cash" doesn't literally mean empty pockets. More like $20-$40. Credit card processing machines sometimes go out, particularly at carts in the parks. A few place have a credit card minimum. I was in Aldi a few months ago. The processing system was down. No debit or credit cards. I was glad I had the few dollars to pay without having to wait. I'd hate to want to buy a newspaper or bottle of water and not have a few dollars in my pocket.
It's customary to tip anyone, including DME bus driver, who handles your luggage. It's not generally allowed to load and unload your luggage under the bus. Resorts which have bellhops don't generally have luggage carts available for guest use. If I know I'll be needing luggage assistance at my hotel, or if I'm arriving prior to check in and will want luggage stored,, I make sure I have enough singles to cover expected tips. You can go into your bank and get whatever denominations you want. You can make a small purchase in the airport and get change in singles. You can ask at the front desk in a hotel. Converting a 20 dollar bills to singles isn't that hard.
I undertand some guests might only have 20 dollar bills and not have currency to tip. I don't agree with travelling without at least a 20 dollar bill, probably more, in my pocket.