The way I use an ebike, having at least seven gears is important. I use my ebike to get exercise and to get around. I ride with little or no boost unless I am going uphill or in a hurry to get somewhere. When fighting a big headwind I really enjoy having electric boost.
Most of the inexpensive Ebikes will be one speeds meaning they do not have multiple gears. This makes it significantly less expensive to build the E-bike. However I am not a fan of one gear E-bikes. You will be very dependent on the motor. The single gear will not be high enough for you to keep up with the motor above 10 mph but will be too high for you to ride the bike without the battery assist. Most people do not get as much exercise while riding an ebike with only one gear.
The Human body is well adapted to walking at about 3 mph. With a 25 pound bicycle and 12 to 24 gears on flat ground we can ride at 10 to 12 mph with a little more work. However when we come to just a slight grade or headwind that speed drops to 3 to 5 mph rapidly.
The huge advantage that E-bikes bring to us is they allow us to ride at 10 to 20 mph with about the same effort as walking. And with an E-bike slight hills, steep hills, headwinds can be overcome by the motor. They take the drudgery out of going up hills on a regular bicycle.
To get up really steep hills and so I can ride the bike home if my battery runs out of juice I need gears on my E-bike. With an E-bike that has only one gear and a battery with no juice I will have to walk it up hills and/or I will not be able to assist the motor when I am riding over 10 mph.