No, it's because you're forced to pay for services not rendered.

That's frustrating for rare users (tourists, etc), but seems optimized for the regular traveler.

The rare user might prefer to buy Exactly One (or two or four) tickets, as they know they won't use the excess. This is similar to the frustration of a first-time user at the bay area ferries, where the process of registration, app installation, etc, is much less convenient than most parking.

The regular user, however, doesn't care as much about the initial overhead, as the convenience outweighs the overhead. A remainder balance on the card is less frustrating than for a tourist, as they know they're going to fill it up again.

That said, it would have been nicer if the transit company had phrased pricing in terms of Number Of Rides, rather than dollars (dollar amounts made up):

  4 rides ($10.42)
  10 rides ($21.37)
  50 rides ($90)
  100 rides ($180)

It is still strictly worse for the repeat riders if they get a card valued at 10.41 than 7.91. The only reason for the city to even allow someone to do it is to underhandedly get more money when someone inevitably loses their metro card.

"forced"