Richard, your comment could sound a bit patronising.
I understand why a heat gun is needed to get the glue to a high-enough temperature. From what I’ve read glue-lined heatshrinks give you extra protection you would need, for example, for permanent outside installation where the antenna would be frequently subjected to adverse weather or chemicals.
As a mainly fair-weather activator if my antenna gets wet, it’s because I was unlucky and it (plus the mast, guying, etc) gets a good drying out once home. I use heatshrinks for extra mechanical support where the coax feeder gets flexed a lot near the BNC plug - a known point of failure. Normal (non glue-lined) ones like mine are fine for that purpose, and a hairdryer is hot enough to shrink the heatshrink to a snug fit.
I would imagine that the majority of radio amateurs do not make such equipment for a living and don’t have access to suitable tools from their professional work. Many doing this hobby on a budget (e.g. retirees like me) cannot justify buying tools they don’t really need or would use only occasionally.