When I was in elementary school, during the 90's, I mostly remember it as The Swedish Flag Day since the town's music school orchestra came and played the National anthem while the flag was raised. When it became a holiday in 2005 I had to google to know why we decided to make 6th of June the National Day. The 3 reasons:
- Gustav Vasa* was elected king 6th of June 1523 which made Sweden, again, a sovereign state
- The instrument of government was issued 6th of June 1809
- First decision on 1974's instrument of government was made on 6th of June 1973
* he's seen as the founder of the modern national state of Sweden
Also, to make it a holiday the government removed Whit Monday as a holiday. A lot of people wanted Midsummer's Day to be our National Day since it has deep roots and is still celebrated in Sweden. I'd say, that would ruin the vibe of Midsummer.
The problem with having a National Day without real anchoring to why makes it just another day free from work. We're not a patriotic people, a lot of people here are afraid to be seen as such since it's often connected to being a racist. You see more people wearing the UK or US flag than the Swedish here. I think though that if our National Day had the same history as in France or the US even the Swedes would dare to celebrate for real. Maybe, we will with time, it's still a very young holiday for us.
Disclaimer: I don't speak for all Swedes, some might celebrate National Day and think it's a great day, some might ignore it completely. This is my point of view.