My 2 cents here. Totally agree with the Sparbrötchen mentality.
I have talked about bunq to a bunch of friends in Berlin. Only 1 guy out of at least 20 people got interested and registered for an account, but mostly because he's also a developer and wants to play around with the API. My girlfriend also joined but simply because it's a joint account. All the others said they see no advantages paying 7.99 a month, when they can get most features for free elsewhere. It might be just my impression, but I think trust and cost are by far the two top priorities for Germans when choosing their bank account.
Trusting online banks is very very difficult - there's no branch where you can see someone face to face, and (usually) no phone lines that you can call. Only chat / email / twitter. And to make things worse, bunq is a Dutch bank with no offices in Germany. Even the NL on the IBAN is enough of a reason to scare some people away, regardless of SEPA discrimination.
And then there's cost. Free = always better. Most "legacy" banks here offer free accounts, and the non-free are very very cheap. When you pair this with the fact that they are usually trustworthy, you have a winning combo - exactly what most Germans want. Everything else (free FX, real time notifications, 25 IBANS etc) are simply nice extras. Open API? This alone made me switch to bunq, but to the casual user.. they probably don't even know what API stands for.
So most Germans I know have a main / salary bank account on one of the big branch-banks, and a free account / card with a fintech to use as a daily / expenses card. And there lies the problem: N26 and Revolut both have way more features than the Travel Card on their free accounts. To really make use of bunq, you need to have the Premium account - but it's a hard sell unless you convince that bunq is very very very trustworthy.
Even if bunq would start marketing aggressively in Germany, I suppose they would need to slightly adapt their free tier to get customers by the numbers, and once convinced (we trust you!) some of these would switch to the paid accounts.
PS: by trustworthy here I mean not only the general idea of trustworthiness. A trustworthy bank won't send you emails saying you have to reverify your ID in max 3 weeks otherwise your account will be closed; won't temporarily block accounts for no apparent reason; won't take days or weeks to reply when you have urgent issues... Even if bunq does not do such things, it doesn't matter as long as some of the competition does. It stains the image of all fintech companies :-( For instance this: https://www.capital.de/allgemein/polizeieinsatz-und-renitente-kunden-der-aerger-fuer-n26-hoert-nicht-auf
TL;DR; join bunq, fight (very!) hard to convince your family and friends to join as well