It is no secret, just look to the Bicycle Retailer article showing the 2018 purchasing trends, that EBikes are gaining popularity. There are a couple reasons that I can see:
1. An EBike extends the range of any cyclist. Sure, you may be fit, but if you want to commute to your place of work, an EBike will allow you to cover a greater distance without being all sweaty and exhausted when you get there. In large cities like DC, LA, Seattle, Toronto, and Vancouver, they are a game changer.
2. Want to go carless? An EBike with cargo capacity will allow you to carry more than just yourself. Think kids, groceries, and even building supplies.
3. Age. An EBike allows for someone in their 60's, 70's, and even 80's to continue to cycle.