Well, KPN is one of the most green and environmental friendly telecom providers in the world. In terms of hardware that means that KPN thinks about multiple things before replacing a modem. How old is the old modem, is it still functional and do we still support it. 
 

At the moment KPN has three modems that it supports, that is the V10, V10A and the box12. All three are good modems which are really stable and KPN thinks that they are good enough for now. One of them only has 3 LAN ports and both V10s don’t have WiFi 6. That is not enough reason for a swap. 
Swapping modems without a reason is costly, environment unfriendly and means you will get a big stock of V10s which are still good to go. 
 

If you want WiFi 6 then I advise one or more WiFi 6 acces points. KPN sells Superwifi 2.0 with WiFi 6 but there are also other manufacturers like TP-Link, Netgear or Ubiquiti

I asked my local garage to update my petrol car to electric. Guess what; they won’t.

That is kind of comparing apple with pears.

But if we wanna stay with cars, I have a lease car with CNG, after six years or after 120.000 kilometers I will trade my CNG car for an electric one because then the lease company determines that I need a new one.

I meant to say that technology evolves. When new technology arrives you cannot expect to throw away the previous generation. WiFi 5 is still excellent for almost all uses. Also WiFI 6 was brought about with lots of marketing, in most home scenarios the benefits are small.