There's a measurable difference between the bonus and no-bonus option, and in this case, that's 5%. That is the offer. Given the option between the two, I'll take the bonus knowing fully well in either scenario they are profiting.
AT&T's classic monthly rates factor in subsidization, and thus are substantially higher than ...whatever value you seem to be wishing that they charge - I sincerely hope not at-cost. If they offer a 5% discount, they're still profiting, but you're paying 5% less than you would have. That is something, and that is an offer.
You're comparing apples and oranges. Compare the 5% bonus with simply lowering the cost of fares an equivalent amount.
The MTA is at least partly-funded by real-estate taxes.
Of course, now that there's the $1 per card fee, it might not be a useful purpose, but that's a different argument.
Hah! That's a good one!
It's like those stores that always have half the store "50% off," they just always charge more and expect you to only buy the things on sale and feel like you got a great deal when in reality you paid what they expected you to pay.
i.e. that "free 5%" you get when buying a card comes is the same damn thing as just charging 5% less on the per ride costs in the first place. It's not free money at all. You just feel like it's free. Honestly, that "free money" only further supports the idea that the MTA is run more like a penny-pinching crony business than a public transport system.