Registering a trademark is generally more expensive than a domain name, and trademarks don't compete on the same namespace and is split depending on industry. The biggest difference to the domain market is that with domain names everyone is clogging the same namespace. If people just spread out based on nationality and industry it would be easy and cheap.

To make a direct example, if I talked about Abba here in Sweden, most people think about the music band. But if I talk about Abba in the context of food, people will instead think of Abba seafood that make Kalles Kaviar and pickled herring. Abba.se as a domain is thus very ambiguous as it doesn't specify if it about food or music, and abba.com is likely to surprise people as it has nothing to do with either.

To make matter worse, companies that want to protect their trademark or work actively at preventing fake shops will often buy several hundred versions of their domain names under different name spaces. It is seen as best practice, especially for online shops.