Teak or no teak...
To me teak decks are a ''lose-lose'' situation in every way. Teak is expensive at time of purchase. Teak requires a lot of maintenance or it deteriorates more rapidly. Teak decks are heavy and their position above the waerline reduce stability. When they get wet they take longer to dry. They are really hot in warm weather.
If you leave them natural they deteriorate most quickly. If you oil them the track oil and become slippery when wet, need frequent attention and eventually ''go dark''. Varnish (or simulated varnish) has its own problems beyond the increased maintenance. Varnish is slippery when wet and breaks down at the edges of the planks.
Then there is the issues of the material itself. When I was growing up, the ''normal'' teak used in boats was Burma Teak from old growth tree. This is the durable species of teak upon which teak''s reputation is based. Burma teak has become comparatively rare and expensive. Today, we see inferior grades and species (angelique and the like)substituted for the great quality teak of the past. I am also uncomfortable with the idea of cutting down old growth forests for this kind of purpose.
Then there are the construction technique problems. Conventional ''laid'' decks leak. Screw down decks are drier down below but it is only a matter of time before the core rots out. Glue down decks have their own problems. In order to glue down a teak deck the planking needs to be fairly thin (3/8" or so). Burma teak, which is denser than the teaks of today, erodes at a rate of 1/8" per decade. Starting at 3/8" thickness this means a useful lifespan of 15 to 20 years vs. the 40-50 year lifespan of a ''laid deck''.
I have no idea why teak decks are popular in expensive boats.