Dextrose tabs have the following advantages over jelly babies and others:
The taste means that one does not so easily scoff down more than is needed and as you have noted high bsls after jbs etc is an issue
The idea of using glucose is to combat low bsls not to get a taste hit
Dextrose tablets give you a quantifiable amount of glucose, not as easily estimated in jbs, drinks etc
Glucose is less ruinous to teeth than jbs etc (which usually have table sugar or sucrose as it is called, in them).
Some sweets/foods may contain fat which may slow absorption of the sugar.
In contrast, to the glucose in Dextro tabs etc, fruit juices may contain fructose which is a type of sugar which may contribute to the formation of fatty liver
It may be worth noting that some of those advantages aren't universally agreed
Re the scoffing - if you need help to avoid scoffing, then yes, the less nice taste of tabs might be worth it, but if you can manage your hypo treats, no reason to not have something nice. See also Jaffa cakes etc.
Re the idea that it's not to get a taste hit - if you can manage it sensibly (ie previous point), there's no need to be puritan about this. It's recommended to not give small children the idea that they get something nice for hypo, because it's quite common to learn to fake it or worse deliberately induce it, but if you're capable of only treating when you need to and in an appropriate quantity, getting something nice isn't a bad thing. (personally I have slightly the opposite problem, I need to encourage myself to treat hypos, and having something nice helps.)
Re quantifiable amount of glucose - so do jelly babies, so long as you stick to one brand, and since there's only one decent brand, this isn't hard
Ditto jelly beans, jaffa cakes, sugary drinks, etc - this stuff is all measurable and controllable.
Re teeth - there is a bit more truth here, but no matter what you eat, good dental hygiene is important. So long as you keep on top of that, then eat what you want.
Re fat - if it works, it works. JBs are often recommended because they're high glucose. They also have hardly any fat in them at all. Jaffa cakes probably have a bit more, but if works for the hypo, who cares?
Re the fatty liver - the amount of fruit juice in a jelly baby is tiny. A 5 JB hit (my portion size when I need it while out exercising) contains the equivalent of 2ml of fruit juice. If anybody is going to say that's enough to cause a fatty liver, I'm going to raise a few eyebrows at them. Sure, there may be problems with excessive fructose in diet. Maybe drinking litres of juice, or of course the US favourite sweetener, high fructose corn syrup. But as is repeatedly said, eating things in moderation will be fine