So how long can this state of affairs continue? The operators will have had up-front costs, e.g. setting up the facility, fixed costs, e.g. staff wages, rental of property, etc. and variable costs, e.g. the quality and quantity of 'raw' foodstuffs, fuel used, etc. They will have calculated a footfall of a certain amount, and an income '£' spend per person. Sooner or later, it is predicted that they arrive at a point where income and expenditure match, the so-called 'break even point', and profits are then made. Obviously the sooner the BEP is reached, the happier the management and shareholders are. From what I am seeing, it seems unlikely that this point will be reached any time soon, i.e. expenditure will exceed income. In cases like this the model is then declared unsustainable, and the business collapses, or the operater pulls out before they go bankrupt.
Solution. Cut costs.
Wages of employees - difficult, 'cos they are probably not well paid anyway, and they'll find alternative employment.
Quality of meals - easy to do, but has a kick back in that footfall/£ spend decreases, and the BEP recedes even further.
Portion size - see above.
Or increase footfall. What would attract greater numbers through the door. How to do this is the real problem.