I think many of us can understand the feeling of being let down and empathise.
To be charitable - you may be projecting such a good image of coping, that they don’t realise, but I agree, people should not have to be reminded how to be a good friend, whether in need or when things are going well. They may also be the type of person who (IMO selfishly) claims they are “no good” around illness.
I think you may need to take the bull by the horns- at a time when you are not feeling too angry or disappointed - and ring them up, say how frustrated/bored/anxious DH is being and how he might like company or distracting so would they (or just the husband) like to pop round for half an hour or so for a cup of tea and cake and pin them down to a specific day or even suggest that one of his friends keeps him company while you have to pop out.
Paw was a much- loved and popular man, but when he was in hospital I could count on the fingers of one hand the men friends who would ever visit him. Then somebody said they assumed I was always there and didn’t like to intrude (as if!)
So I see exactly where you are coming from, your expectations are absolutely not too high and you would certainly behave in a more considerate manner in their shoes.
So swallow your pride (and your true opinions which I would share) and give them a nudge, your DH need never know and they may even come round to being true friends. 