Well, that's the assumption isn't it - that it's all because of the recession. But the figures show that for half of those 58, the decline set in from 2004/2005/2006, before the recession hit.
Very true - when the lo-co phenomenon started there was a rush to open bases at small airports, where often the airport operators gave sweeteners to entice the operators in. After a time, when the sweeteners ran out, the airlines discovered that the yield simply wasn't there, and retrenchment began, so places like Coventry, Teesside, Doncaster, Blackpool, Newquay; and most recently Prestwick, fell out of favour.
Even larger airports, such as BHX which hit bad times in the recessionary years is only now returning figures near to their peak - and that using larger equipment, so I guess (though I haven't checked) actual ATMs may still be below their peak.