Not something to do with the failure to let them perhaps?

A certain amount of retail and commercial, and office space is often required by planners in mixed use developments. When I worked on new housing developments in Hackney the planners required us to produce B1 space which we knew would not have a market hence it remained empty and produced a financial loss against the scheme. It seems sensible to produce retail units but not necessarily everywhere. The issue therefore requires careful market analysis. I doubt if developers are leaving these spaces empty deliberately as they need to assume a certain level of return at appraisal stage and vacant premises hits their pockets hard.

Forest Hill is not East Dulwich where despite the recession there appears to be very few vacant premises in Lordship Lane due no doubt to the gentrification of the last decade.

At least the premises are not unsightly due to the hatched hoarding and are at least there is a provision there in case of any potential improvement in market conditions in the future.