Usually (like almost every single time) someone says anything like "i can only go 100 miles on a charge" they dont have home charging, or dont charge every day, and seem to have an opinion that "my car has 230 miles range, I only drive 20 miles a day, I should be able to charge every 6-7 days or so".
Very rarely its something else, but I feel pretty comfortable predicting that based on that statement, this OP doesnt charge every day for "some reason", either because they dont have home charging, or they think that its better for some reason to run the car battery down before charging it back up.
In reference to your incorrect assumption: my car is plugged in at home every day the instant I get home till the instant I leave per the recommendation of an engineer. It is almost never driven below 10% charge and is always charged only up to 80% unless I plan a rare long-distance drive of 100 or more miles, in which case I do a full charge the night before. The mileage estimate of 1% charge used per mile is based upon a few of those long drives on highways, not short and in-town frequent stop drives.