They must see some way of making money out of empty properties - and the only way I can see is as residential development opportunities. Not necessarily by hoping for Councils to allow planning use classes of existing building to change - as recommended by a right wing think tank last year - but waiting for a larger scale development of an area into residential, e.g. the current development of 255-269 Sydenham Road.
If so, it means that the way to save High Streets is to ease the general supply of housing, allowing developers to build - at higher densities - in existing residential rather than retail locations - preferable building higher than more cramped.
The background can be seen in this chart

from which it is clear that the recent decline in house completion is not so much to do with the credit crunch as part of a long run decline. In fact, like most UK corporates, I think house builders have quite strong balance sheets, so could build more houses if allowed.
The obvious culprit is our planning system restricting supply, with several inevitable consequences. First is that only higher margin development happens - e.g. for the rich. At the lower end of the market, people just have to pay up until such time as they get to the top of local authority waiting lists for social housing. Then people who do have social housing - at more affordable rents - have an incentive to sub-let , living happily albeit illegally off the excess rent our planning policies cause.
Only too believably, our government's response to the problem is to criminalise such lower class entrepreneurs; the alternative is too awful to contemplate - a further serious reduction in property prices

with consequent pain from the pages of the Daily Mail - and perhaps more seriously mortgage lenders.
The Labour Party response is to say more affordable homes had to be built, which is absolutely correct, but begs the question why it didn't happen between 1997 and 2010.