Cause if you're a tourist you're expected to spend money and a small price hike compared to locals won't impact your decision one way or the other.
I also had this reaction a couple of years ago when my city started to introduce special touristy pricings, but nowadays I don't think it's a bad thing. The local government introduced a special "city card" which is essentially a museum card + hotel discounts + free public transport (within the city) + cheaper or free access to all touristy spots. If you travel on a budget, you just have to jump through an overtly advertised hoop, and if you can't be arsed to do so you end up paying a little bit extra. Locals don't have to bother, as showing our local ID is enough to "unlock" lower pricing. Win-win in my book.
pensioners should pay less because they have less income and are more dependent on public transport.
tourists paying more doesn't make sense, because tourists are not going to use this kind of ticket anyways unless they are in germany for a few months. and even if they get it for just a short visit then they will hardly make as much use of it as locals, so there is no benefit for them paying more.
that said, there could be a more expensive version of this ticket that does not require a subscription that you'd have to remember to cancel.
> pensioners should pay less because they have less income and are more dependent on public transport.
Less income than who? Twenty-somethings? I doubt that. More dependent? Many pensioners have cars. And they, by definition, don't have a job to commute to every day.
young pensioners in their 60s maybe, but the older they get the less likely they are to drive.
more than 20% of single (or widowed) pensioners in germany have less than 700€ per month.
only 40% of couples get more than 2500€ per month (that's more than 1250€ per person). the rest is somewhere in between.
so yes, pensioners do have less income. and twenty-somethings get student discounts.
especially very old people are often isolated and depend on public transport to get around.
I imagine this model will attract quite a bit of additional tourists (without their annoying cars), which is a good thing (for most cities).