I really have no "problem" with those that use the transpose button, but I personally try to avoid it for a few reasons. First, I'm a music theory nerd and enjoy trying to play everything in in all 12 keys. I do this for fun everyday.

Some notes and chord inversions don't sound right when transposed out of their range.

When playing two keyboards, which I do often, it can a PITA to have them both set up to transpose. Also, I hate it when I forget to turn off the transpose button, and start the next song in the wrong key, and all the confusion that can cause on a live gig.

Sometimes I play with musicians that like to look at my hands to figure out the chord changes.

And what happens to you folks that play everything on your KB in C, and an opportunity comes up to play and sing on an acoustic piano or keyboard that has no transpose bottom? I hate making excuses.... So that's why I prefer to learn to play in the correct key without the aid of a transpose button. With that being said, I think the transpose function is a great feature and I'm glad it's an option.