They have the ability to look at your accounts to see if you have additional inflow if cash for example from second homes and not declaring it to HMRC. They can also see if there is money being received that could be tracked to illegal iswsvsucjvas drug money , yes who would be silly enough to put that straight into a bank ...but , also they will be able to see if money is being sent regularly overseas for example Thailand and wallop pension frozen ... So there are a few reasons they will be looking even if you are not on benefits ....