On the other side of the pond just Nieuw Amsterdam (currently New York City) urban area has significantly higher population than the Netherlands. Since practically there is no single telecom market in the EU, ISPs face an order of magnitude smaller problems on the East side of the Atlantic.
While being so “advanced” those ISPs still use the CPU cycle intensive PPPoE instead of the CPU cycle frugal DHCP for accounting.
Actually @NathanA has just given some very real reasons of the advantages that dynamic IP addresses may provide for an ISP. Whether the cost savings result in lower fees for their customers is a different story.