As most servers will tell you, a tip in cash is always preferred — but the realities of our collective move to a cashless society mean that most people accept that tipping in cash isn’t always possible.
Cash has historically been the preferred method of receiving tips for service industry professionals, because it meant you were able to take those tips home at the end of the shift rather than wait for the credit card tips to settle and be paid out later. This would then also allow for a nightcap or two with colleagues to be paid for by said tips. Revelry would ensue.
But with more establishments either moving to credit cards as the main form of payment, or choosing to pay staff a living wage by placing them on salary and removing tipping entirely, cash tips have become much less common than they used to be. The most important thing now is that if you are given the opportunity to tip, you tip. Fixating on what’s better, cash or card, isn’t as important as taking care of the staff that served you in the first place.