Well, I'm not going to defend the actions and moods of Dutch ATC controllers here. I generally find them very accommodating, provided that you come across over the radio as someone who knows what he's doing and knows what he wants. (And yes, I have flown straight through the Schiphol CTR on a number of occasions, routing and orbiting exactly where I wanted to.)
I'm just saying that if you conclude that the Dutch ATC doesn't have/use mode-S simply because they, on occasion, give you a discrete squawk, you're wrong.
And there's something else that I learned from discussions elsewhere. A mode-S data block on the controllers screen occupies a lot of screen real estate. Callsign, squawk, level and some other bits and pieces lead to a lot of clutter. Apparently one of the filters that a controller can apply is a filter that reduces the data block for each 7000 squawk into the pre-mode-S squawk and FL only. Maybe that's the reason for asking you to ident. Or it's just old habits dying hard, who knows.
Like handing me over to Langen 20 nm before border, other times I have to initiate request.
Well, legally speaking whether they should hand you over or not depends on the level of service you requested. If it's an ICAO Flight Information Service (like Basic Service in the UK), you cannot expect them to have radar and you cannot expect handovers. So it's up to you to announce that you're leaving the frequency, usually combined with a position report ("approaching the FIR boundary north of Nijmegen, two thousand, switching to Langen"). If the controller is not that busy and has radar, sees that there's not more relevant traffic for you and decides to arrange a handover to Langen, well, lucky you.
That's the fun about flying VFR in controlled airspace - roll with the punches.
Some airfields in the Netherlands are fussy about Noise Certificates, otherwise, they charge dearly for the landing.
They have to. It's in their planning permission ("gebruiksvergunning").