I am asking why it is that doctors always tell me to eat fruit,
He's probably following the NHS advice to go for 10 fruits and vegetables per day rather than five. Advice given with the "one size fits all" attitude and encouraging the "keep taking the tablets" attitude that some might have. Of course everyone can do exactly that, it's their prerogative. However, if watching carbs, it's not so straight forward. Perhaps you should ask him "which fruits?"
I did have a list of fruits with the lowest carbs (
https://www.verywellfit.com/low-carb-fruit-list-2242528, a cup = 340gms) but when I double checked the values, they didn't agree but they are still lower than most fruits.
These values are not from that list but checked individually. Grams of carb per 100gms in brackets.
Lime (11), lemon (9), rhubarb (4.5), apricots (11), cranberries (12), guavas 14), raspberries (12), kiwi (15), and blueberries (14), strawberries (8). Water Melon, canteloupe, honeydew melon are also low.
For me personally even strawberries will cause a slight elevation of BG, but we'll all react differently.