OK, I'll fess up.
My neighbourhood is not leafy or suburban, it's the sort of densely-populated that place people commute through from the suburbs to the city centre: in fact, a high proportion of the traffic consists of through-motorists rat-running through traffic-calmed (ie narrowed) roads to avoid the motorway and the two A-roads that are their direct route in and out of the city centre. The rest is buses and HGVs coming off the motorway into the industrial estates that half-surround the neighbourhood. So the traffic at certain times of day is "light" but frequently speeding - and with a high (self-selected) proportion of impatient drivers.
There's a few hundred yards of mixed pedestrian/cycling path here and there that all end - invariably - at the worst possible places, often for no discernable reason, and often on a high kerb. There are fragments of on-road cycle lane on one or two of the A-roads which, again, invariably disappear just where the going gets tricky.
I'm a beginner cyclist and new to being a road-user. I need to study each road layout anyway, before I can use it confidently and safely. So sometimes, when the white line turns off the pavement straight into the traffic accelerating off a roundabout or whatever, or when I can't make out at the time quite what a cyclist is expected to do, I just carry on down the pavement to find a safe place to enter the road. And sometimes - shock horror - I just carry on cycling another mile or so. I've encountered a handful of pedestrians in all that time - no-one seems to walk any more.
I've found motorists annoyed at me being on the roads or on pavements (mixed/use!) about equally: and I've found many who are willing to be tolerant. As they pass me labouring up the pavement beside the A-road, I'm pretty sure many drivers are happy enough that I'm there and not in front of them. I would have expected cyclists to be more understanding of why some people do cycle on pavements.
I don't ride across pedestrian crossings or amongst pedestrians: in fact, I encounter far more pedestrians on the cycle part of the mixed-use paths than anywhere else, because these are (a) maintained and (

within a few hundred yards of new shopping developments.
Some of the routes I have to take are long hills that I can't hope to climb at more than a few mph, much to the ire of motorists (and by the sound of it, the contempt of cyclists like you). So yes, some of us pathetic wobbly wimps do sometimes ride on deserted pavements instead of constantly getting off to push. And I'm not apologising for it.
It's not something I'm particularly proud of, but for someone who's inexperienced, not particulalry fit - and a shrimpy weakling at any time - it's a necessary transitional (I hope) phase.
For me, now that public transport's been priced out of my pocket, it's the only option for mobility and for load-carrying beyond walking distance. It's the difference between being confined to a couple of square miles most of the week and having a few choices in life - like where to buy food, or buying clothes at all.
For others, getting on a bit in life, or with various ailments, there is no feasible option to a bit of intermittent pavement cycling. Not until the roads become a lot more more cyclable, anyway. We're not all ****ing road-warriors.