I doubt there's any use at all for the casual user. Except for the lengthy covid interlude I'm a pretty frequent visitor: I use TnG as a a travel card getting me through the public transit gateways quickly. Top up is simple at metro stations paying a 50sen fee at ticket windows, or using the TnG-friendly top-up machines (now many more of these are available).

I understand registering the card could be useful to residents, or others, who might use the card more widely and maintain significant balances on it.