The four officially recognised minorities differ from other minorities by their status as ethnic groups with German nationality and a language of their own and by being autochthonous, i.e. having a century-long history of living here. See statement of the
Ministry of the Interior. The Danish minority in Germany obviously isn't threatened culturally by the majority, since they have the backing by the neighboring country, and the language is not at all in danger. The Friesen and the Sorbs, however, both are estimated at about 60,000 people. The transmission of the idiom from one generation to the next which worked for centuries wouldn't be assured nowadays without extra assistance and – also financial – help.
I don't know if the 8 million € of funds for the Sorbs are too much – after all, it creates jobs and is additional support for not exactly thriving regions. It might actually be a good strategy to help strengthen the attachment of people to this region and slow down migration of young people to the western Bundesländer.
The "Economist" article mentions that the Roma only get 1,6 million €. That is indeed a remarkable discrepancy. I guess this might have to do with the fact that the Sorbs are represented more efficiently (by the Domowina), maybe also with the DDR tradition, when they were promoted for the price of political loyality. Preserving the mainly oral culture of the Roma, who are fragmented in subgroups, is probably also much more difficult.
BTW, in German there is a distinction between Roma and Sinti. The latter have been living in Germany for about 600 years. In the 19th century, Roma groups arrived from South East Europe, and then recently more, mostly due to the Balkan wars. Some Sinti seem to insist on the difference between them and Roma, they also have their own organisation. See
Sinti und Roma. In my 1st class in elementary school in a small Franconian town, there were two Sinti siblings. They were later sent to the Sonderschule, because classes were large, and they didn't get the necessary extra assistance. I googled for one of the class mates, and found someone with the name who is a scrap metal dealer – that is probably him.
There is another group of traditionally itinerant people in Switzerland, Germany and Austria, with a slang of their own (not a language like Romanes/Romani) – the
Jenische. They are comparable to Travellers, Tinkers or "
Pikeys", I guess.