They work and they're better for some niche applications, but for ordinary everyday riding, like shopping, commuting and touring, they're a long way behind geared hub-motors.
When nearly all ebikes were 36v and 15A max, the hub-motors struggled for power on any sort of hill, but now that we have decent sinewave controllers with current control running at 48v and whatever current you want, crank-drives lost their advantage on climbing. Now all they have is disadvantages on comfort, convenience, noise, cost, running cost, durability, reliability.
I think crank-drives are generally easier to install, but why would you want the short term gain of saving a couple of hours installation time at a cost of suffering years of torment with a sub-optimal drive system.
My hub-motor has been going for 10 years now and has been perfect for my needs. I keep looking at alternatives. I have enough money sitting in the bank to buy any ebike I want, but I haven't found one that beats it yet. I'm pretty sure that if you tried it, you'd come to the same conclusion.