Indeed, the main problem was that Wilhelmina kept him out of most things related to her work. He never had a clear role, or many things to do. Neither did he have his own appanage (he had to ask money from his wife), which became a bigger problem when the money from the Grand Duchy of Mecklenburg also dried up and he had to support some relatives too. After that he always money problems and people actually were afraid to sit next to him with dinners as he would probably ask for a loan. This wasn't helped by his private conduct as he was an easy pray for blackmailers. It has been established that he had several children with Mien Abbo-Wenneker and the story goes that he went to (male) brothels and that the high society of The Hague kept their children home when they knew that Prince Hendrik visited the scouting organisation (of which he was a patron). It is also suspected that ueen Wilhelmina's miscarriages were probably caused by venerial diseases from Hendrik. All in all a sad life, he must have been a very unhappy man. He once commented about himself: 'ich bin nur das gepack', I am only the luggage.
At other courts the life at Dutch court under Wilhelmina was well known, which was one of the reasons why it was difficult to find a husband for Juliana. The Dutch prime minister at the time also saw the problem and didn't want to repeat the Hendrik scenario. Her husband Bernhard immidiately received his own money from the state and got a clear role. Sadly in the process they may have given him too much freedom though.
When he died some joked that the prince was like the colours of the flag. His hair was red, his funeral was white and he was as blue as a rabbit (the latter being an expression to refer to drunkards).
However, Queen Juliana always said that he was a wonderful father, and that they enjoyed being 'naughty' together. And that he and her mother allowed her a lot of things that many other parents would never allow. It is a pity that up to now nobody ever wrote a biography about the prince (or about Queen Emma for that matter).