If it was an option in your country, would you pay your taxes with Bitcoin?
Let's do a small calculation.
Take a medium-sized country in Europe, say, France. About 60 million inhabitants. If these 60 million people paid their taxes with bitcoin, then that would mean: 60 million transactions. At a rate of 3 transactions per second, that would mean, 20 million seconds. 231 days of full blocks. By the time your taxes are paid, using the FULL BLOCK CHAIN, you can almost start over again
France is one of the biggest countries in Europe
In fact, by the size of its population it is ranked the second most populous country in Europe, after Germany (if we exclude Russia from consideration, though its European part would likely still beat any single country in Europe). Further, not all 60 million people will be paying taxes, you should obviously exclude the elderly and infants. Other than that, Bitcoin scalability issues are well known just like the ways to solve them, so it is not so much scalability issues themselves as miners hindering further Bitcoin improvement in this direction. For example, Lightning Network would make such issues virtually non-existent (as well as solve a whole bunch of other problems, e.g. lack of a decentralized exchange)