Hello there. 
Can anybody tell from firsthand experience if they ever had a real practical use or need for the Maestro Card? Like for example a country or some use cases where “only” a MasterCard was not enough?
What benefits are there for a Maestro Card that I wouldn’t have with a MasterCard?
Thanks 
Only real advantage (for me) I have ever seen with maestro is that there is (was?) some online merchants which lower airplane ticket prices if you pay with maestro. But usually normally nobody even allows you to pay with maestro online.
For me MasterCard clearly wins over Maestro. As I said before in my country (Latvia) Maestro and Visa Electron are mostly seen (used) as cards for students and pensioners.
If you are in some countries such as Netherlands, Belgium and Germany, away from the major cities, local merchants may only accept Maestro and V-Pay, not MasterCard or Visa.
I’ve personally been caught out in the Netherlands in a restaurant in Rotterdam by this.
I’ve also come across ATM machines in Canada that only accept Visa, not MasterCard.
If you might find yourself in this situation and the app is offering you the different options, may be worth getting them as backups.
Elsewhere, I’ve personally not had any problems with the MasterCard, but there could be other areas where only one of the options are accepted
Austria also in my case. In a few small groceries stores and restaurants, I need to pay with my backup V Pay card from my traditional bank. It would be great if 
will give a chance to order Maestro for everyone, even if only for extra charge for issuing.
The same happened to me in Rotterdam in a Surinamese joint. At the time I only had my French Visa Premier with me, and no cash. Luckily I was with my girlfriend at the time, she waited at the table until I walked like 10-15 minutes until I could find an ATM.
And a similar situation happened to me in Köln, Germany, though I had some cash with me.
I travel occasionally to this area so I would love to get a Maestro, but I do not travel there enough to bother opening a specific bank account just for that.
This is why the ability to chose a spare Maestro card would come really handy.
(Actually I would love to have the 3 options: the same account with one main Mastercard, my Metal card, and 2 spare Visa and Maestro cards, but I cannot even chose a standard Visa with Revolut, even less a Maestro)
But V Pay has nothing to do with Maestro, right?
Yes and no, usually when maestro is accepted also v pay is (talking from my own experience only) but typical MasterCard / Visa is not
V Pay is like the Maestro of Visa I guess.
I can confirm the requirement for Germany as well as there are business not accepting credit cards at all but Maestro was ok.
I already have an EUR Maestro Card from my other Bank. So my question is, are there other NON-EUR countries where a Revolut Maestro makes more sense than a MasterCard for example Russia, Africa or Asia?
Russia you will be fine with Mastercard or Visa AFAIK.
Same with Asia, although some parts only take Visa from what I’ve heard. UnionPay is probably a better choice in Asia outside of countries like Japan and South Korea.
Not sure about Africa but I’d say its probably the same.
So yeah, just central European countries.
Maestro is MasterCard, Vpay is Visa.
When they accept MasterCard, they’ll accept Maestro Most likely.
Switzerland has some tendency toward Maestro but not many don’t accept credit cards if they accept Maestro/V-Pay.
I disagree on this for NL & JP.
In Denmark there are places where foreign Visa or Mastercard are taxed with a 1-3% fee. Only local cards are not taxed.
Is it even legal to do so?
This is only true in EU countries.
They can not do that with non-business cards issued within the EEA. It’s forbidden by PSD 2 regulation. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32015L2366
I’m not sure there is a general answer to this. It probably depends on the country. Here in Switzerland there is no official law against it but the credit card companies or better the brand’s behind it try to force it by putting it in the acquiring contact to not allow it.