That's often certain German cars in the US. IE some shops will just not work on modern Minis. Plenty of shops will avoid weird, niche cars.
Any mechanic can fix a Citroen, but is it worth the floor time it'd take to get the parts and figure out french quirks vs working on something they know that they'd make the same money in a third the time.
Having done shade tree work on various cars, I'd totally turn down any Subaru engine bay work if I was already close to swamped.
Once upon a time I was the proud owner of a third gen RX7, proud that is until the powertrain warranty ended and I had to go outside the dealership network for minor repairs. Basically your options were... go back to the dealership and pay unsubsidized warranty rates (double or triple what independent mechanic charged for "normal" engine work), or go to questionable looking characters running "performance" shops who wanted to side port everything they could get on a lift. And still pay double or triple the normal mechanic rate.
Any mechanic can fix a Citroen, but is it worth the floor time it'd take to get the parts and figure out french quirks vs working on something they know that they'd make the same money in a third the time.
Having done shade tree work on various cars, I'd totally turn down any Subaru engine bay work if I was already close to swamped.