Because with gas checks you have to make multiple attempts over several more months to try to get the cust to book an appt before then applying to court for an access injuncrion which takes many more months to come through. It would be easy for those legal processes to take a year, especially with the court system delays currently. We're putting cases into court now and they're being scheduled for feb and march 2023!!
I cant speak for the police, but as a housing officer I've found dead customers and they do slip through the net. You have to remember, each housing officer probably has a patch of between 4000-9000 properties each if they'rea big landlord. And on the one time i arrange a forced entry due to a welfare check, the cust hauled us over the coals and complained to the MP. Apparently it's no business of ours why she wasnt answering her door or collecting her mail from her mail box.
Whilst I think its terribly sad what happened, and I dont know what happened with the police, from a housing perspective it's not that simple to just gain access, legally.