This anecdote raises a few issues.
1. Not speaking Danish does not severely impact a job search in Denmark. Jobs from serving in a bar to working in an international company will be happy with an English speaker. There is a small language barrier but not anywhere near as big as e.g. Germany/Italy/France.
2. Denmark is definitely a country where two incomes are needed to live well.
3. The wage disparity between low and high status jobs is not that high. So if the second income is low status it will still make a big difference to household income.
4. Were your friends from outside the EU? There may have been a non language related reason for the wife to be unable to obtain work.
5. The Danish government provides free language lessons for foreigners living in Denmark - although the language is difficult.
6. Academic salaries cost of living adjusted are far better than in e.g. UK (but not as good as those for senior people in the USA).
7. At least your friend was a lecturer... In other countries their role could well have been filled by temporary staff. The Danish have rules preventing the eternal post doc situation that has developed in the UK and US.