I do think the answers from NextLevel should have been sufficient. The answer from Wister was perfectly adequate as well. But....
Why do so many tennis players in today's pro tennis game use a 2 handed backhand?
If you do seriously play racket sports, this is not a real question and the answer should be obvious.
Even in a sport like tennis where you have a lot of time and can turn your feet, your hips and your shoulders fully to power into the ball without compromising your position for the next shot, the strongest one handed BH is nowhere near as strong as a normally strong FH. A BH can be sharp, precise, pinpoint, and have pace. But it will not have the same kind of raw power.
And because of this, most top tennis players use a two handed BH these days.
In TT, your feet are either neutral or turned slightly towards the FH for the shot, or you would be seriously compromised on your FH. This means your hip rotation happens while your legs are still turned towards the FH. And most of the stroke happens in TT with the hips, the elbow joint moving the forearm, and the whip of the wrist. The legs are turned towards the FH so they cannot help as much.
But even if you had time to turn your feet fully to the BH, turn your shoulders and fully use your legs, hips and shoulder/upper body, it still is not as powerful as a FH where your arm is moving towards your center line, while with the BH your arm is moving out away from your center line.
When Langel posted the videos of various sports, especially boxing, he had a very good point. How many backhand punches are thrown in boxing? And why don't they use that as a punch?
Just think about it and you should be able to answer your question. It might be good for shock and quickness? Ali used to use something like a BH flick for his jab. But you will never do damage or knock someone out with that fly swatting flick.
Over the table in TT, that flicking motion is very effective and the FH cannot get that much motion in that short a swing over the table where the table is in the way. But once you can drop your racket lower than the table, the FH has a much larger range for power.
And NextLevel's point about power zone and hitting range on BH and how much smaller it is really should be understood. It is much more possible to make a powerful shot without being in the precise position with FH. If you are not in just the right position with BH the shot is much more compromised.