Can you afford to pay a mortgage for several months on a property you’re not living in? Lots of people can’t & some of those will be people who own a house they’ve needed to rent out. Not all landlords are purely landlords doing it as a business.
The landlord's financial situation is not the tenant's problem. They're problem is paying the rent and finding another place to live when given notice. It is their home whilst they are paying the rent, it's space for hire. A business transaction. And they don't have to allow viewings.
We stopped allowing them because the EA's are dicks who treat tenants like shit. Every one of them. They'd say they were 'just round the corner' and wanted to 'pop in' when we were in the middle of dinner/sex/in the shower, etc., come in with their key with no notice (this is common), pull us up on the flat not being 'viewing ready' or having packed boxes out (hello, we're moving), even had some who expected us to do their job showing the viewers round! Bullshit the EA arranged with the tenant and the tenant cancelled, more like the lying EA never bothered to schedule anything, chanced their arm and got knocked back. EA's lie through their teeth.
We even tried offering one weekend afternoon for viewings or an evening or two during the week. Nope, they all pulled stunts like this. Basically just wanted to keep coining in the rent whilst they sold. Got sick of it and said no after a while.
Then you have snotty viewers 'Can't you go out and 'grab a coffee' whilst we look round?' Nope. You're the 4th person who's been in here today and I don't want strangers pawing round in my stuff without my being there. Nope, don't trust the EA for shit because they're lying ratbags working for the LL.
Jessica's right, you can't really be a decent landlord if you are sailing that close to the wind financially, but hey, blame the tenant.
Just find another house to buy.