I'm not sure how you're calculating that, but when my wife did the math she ended up ditching the 25% card because it would have only been profitable for her if she took at least one trip a week.
I guess you're thinking ICE (inter-city high speed trains) not RB (regional transport)? I guess at >€100 per ride the numbers work out but most "normal people" I know think of ICE as equivalent to travelling by plane, i.e. something you may do for vacations but very much out of the ordinary for regular travel.
> in my experience only people travelling with DB once every one or two years are complaining about it
I take a two and a half hour commute roughly twice a week (in addition to a daily tram commute of half an hour or so). There's no direct route and one of the two stations isn't serviced by ICE.
I could take an ICE to the interchange station but that would barely save me any time due to the long transfer wait, so instead I'm travelling by RB or RE.
The trains haven't been replaced in ages (I'd say on average at least one door is out of order on every train I've used). The RBs often don't even have working toilets. Outside periods with extremely light traffic there is generally not enough seating to accommodate all (2nd class) passengers (though 1st class is nearly empty because there's no practical difference between 1st and 2nd class service outside ICEs).
And of course trains are routinely late or delayed. Delayed trains often add insult to injury by being delayed further when they have to wait to be overtaken by an ICE. So because I know I have to switch trains I always plan for an hour longer in case I miss a connection or end up having to switch trains again.
Let's also not forget that unlike with long distance busses, "WiFi" doesn't mean "Free WiFi". There's only WiFi on the ICE and it's decidedly not free (nor significantly better than cellular) and requires you to jump through hoops if you're not already a Telekom customer (which seems anachronistic in the times of Freifunk & co).
I'm very happy that UK's National Express recently started servicing two lines in my region (RE7 and RB48). Their trains are brand new, they waste very little space on first-class seating (which is still enough for the few people travelling first-class on REs and RBs) and they provide wall outlets for charging laptops and mobile devices.
DB's ICE lines may be somewhat laudable (though still disappointing compared to the Thalys) but DB Regio's service is ripe for disruption.
Let's also not forget that DB has a track record of letting stations and infrastructure fall into disrepair to cut costs, especially the smaller stations not serviced by ICEs or ICs (which btw, look about as vintage as Locomore).