My main reasons, as far as reason goes, are for health and to reduce the cost of transportation.
To fill that in a little, I have COPD and so the choice for me -- I'm glad it's not for you -- is ebike or no bike. With an ebike I can up the assistance when my breath gets short, dial it back down when I've recovered. With a pedal bike, I'd have to just stop, often in precarious places. That's a no-go for me. Now, instead of depending on a car or motorcycle, I've regained mobility that I didn't have before the ebike. And my cardio conditioning is improving. I can do many things without gasping for breath that I could not have done, pre-ebike.
Cost of transportation: we sold one of our two cars. 8 months with one vehicle so far and it's been no hassle. We're both retired, which makes it easier. We both work part-time so commuting is in the picture, but not every day. We go to doctor's appointments, grocery shopping, to visit friends or just to enjoy a meal at a restaurant on our ebikes, instead of driving the car.
But that's not what you asked about. No matter what reasons we have, no matter why we're on the ebikes at any given moment, it's always fun. Hella fun as the kids say. We enjoy the ride, we enjoy seeing bits of nature you wouldn't see from a car, we enjoy the fresh air and exercise, we enjoy the time together, we enjoy the way the bikes give that extra boost of power when you want it, and so on and on and on.
I used to ride pedal bikes a lot -- I was a bike messenger in San Francisco in the mid-70s, a bike commuter in the 80s and 90s, and enjoyed bike touring from high school on (especially bike camping), so I'm no stranger to the fun that pedal bikes offer. Ebikes add a whole 'nother dimension to that. I'm not sure I can explain it, but I know pretty much everyone here on this forum already knows what I'm trying to say.