I think it's worth bearing in mind that most home owners don't expect to decorate every year - maybe one room every couple of years at the very most, but IME years drift by before people get round to it.
Now I know it is not the same in a rented place, BUT it makes it hard for a landlord who is not a professional landlord (eg they just have one or two properties) to start thinking that they should treat the rented place differently. The incentive for redecorating comes between tenants, to make the place more attractive at a higher rent.
and the relative 'attractiveness' of parquet versus carpet, for example, probably wouldn't begin to justify the expense of restoring it.
Also, there simply may not be the funds for redecorating. If the landlord has a mortgage, there may be only a couple of hundred ££ left over each month, which goes immediately on landlord's insurance, repairs, etc. A new bathroom suite for example - yes, you can buy one for £500, but the fitting, replastering, retiling, and repainting will take you up to £2,000 minimum. That could represent an entire year's surplus of rent over mortgage - what if the roof needs fixing? and where's the profit?
Of course none of this applies to landlord's repairs, they simply have to be done as soon as they are required, and lack of money is not an excuse.