Re: 4 One-Handed backhand players in Halle semis.
It doesn't really pay to play with a one-hander in the modern game. The advantages that come with the two-hander in terms of ability to deal with high bouncing topspin and solidity on return are massive, the second being perhaps the most important factor of all. Quicker preparation helps too. At the same time, several of the traditional advantages of the one-hander are a lot less useful than they used to be. Better striking of low-bouncing balls and better transition to the net are of limited value to modern players.
Why spend more time to develop a harder stroke that is realistically probably going to benefit you less than the alternative?
That said, I love the one-hander. Being ambidextrous my coach always wanted me to play a two-hander, but since my idols were Edberg and Cash there was no way he was ever going to convince me. Growing up in the early 90s, the 2HBH was still a shot for girls.