Exactly, and that is likely to be a very small number of lines. It is not sensible to be maintaining swathes of redundant infrastructure all over the country in case one of them happens to be one of those very small number. Of course it will depend on cost of maintaining vs. cost of demolition etc, and any obvious cases of re-opening should be assessed sympathetically.Reopened lines need to have a good business case to underpin the decision to proceed in the first place, which suggests they won’t be a “socio-economic drain”.
Unless it has a very good business case (and thereby restricted to a very small number of lines) then the revenue will probably struggle to cover the operating costs and there will be precious little for maintenance (which would have to be covered by subsidy). Re-opening lines with likely good business cases are going to use a tiny amount of current redundant infrastructure.And how exactly would a reopened railway contribute “no revenue”, unless it was proposed for it to be free to use?
Not that I am suggesting that former rail infrastructure should be needlessly demolished/infilled etc. If it genuinely is cheaper to maintain rather than demolish (and there is no other use for the infrastructure footprint, such as road improvements, development etc) why would you do that ? (apart from the liability to do the maintenance, and at some point major work is likely to be required.)