This is the issue, at least for me, I have an appointment made for me, and as they've not bothered to actually clue me in so I am totally unaware until the day comes and I'm either in and they knock, or out and they leave a card that tells me I've failed to provide access and a nice list of concequences for that like court, turning the gas supply off and eviction.
I know it's due in a certain month, but short of never leaving the house for that entire month, if they don't tell me when they're coming how on earth can they expect me to grant them access? And I have tried to contact them to arrange in the month before and I'm told they contact me, when I say they don't until they turn up and then threaten my tenancy if I'm not in, I'm told they often drop by if they're in the area and you can rearrange if you're not in - absolutely fine, they have caught me in before like this, but, if I'm not in then don't start threatening stuff - just a 'We called on the off chance and you were out, please call this number to rearrange'. If you don't, or you don't keep the appointment or rearrange then is the time to start saying well this needs to be done and there's concequences if you don't arrange something.
Oh and it has to be someone named on the tenancy present for my ha and that's just me, because I have to sign for it, and yes, I've had more than one no show for these appointments and other appointments - one was while another contractor was actually there, the jobs were conveniently arranged for the same day (absolutely great and much appreciated idea!) Only one didn't show and then I got told I hadn't granted access and would be charged for the missed visit - until I sent copies of the paperwork of the first contractor showing that actually I was in because they were already there and that guy was there for the entire time of the window of the supposed second visit.
It's not hard to treat people decently and actually give them the opportunity to comply with you and not make stuff up. I pay rent, I'm paying for a service, people would be up in arms if you got that sort of service from anything else you were paying for, but HA tenants? Nah, they don't deserve to be treated decently.
It's like a home owner ringing an electrician, they say they'll come out that month, fail to provide you with a date or time, turn up whenever and then charge you for the appointment anyway. Can't see many people accepting the concequences in those circumstances.