Teak and other 'woods' need UV protection as its the destruction of the surface wood cells that causes the coating failure. Urethane varnish, Honey teak, Cetol, Bristol, and just about all other 'clear' coatings have UV absorbing compounds that prevent the wood cell destruction. Without the UV absorbing compounds 'your' finish will probably last only a few months.

BTW - When you divide the cost of Honey Teak by the years in service, its probably the cheapest and least labor intensive of ALL coatings. Honey Teak is a bitch to apply correctly and has a high learning curve .... but probably the cheapest when you amortize over the 10-12 years that it will last. It does need some 'maintenance' clear coats in between.