That just isn't the case
All jobs that come in are prioritised by threat, harm & risk. So, an ongoing domestic incident will always trump most other things and go on as an emergency with an immediate response.
If the threat, harm & risk is lowered - so a domestic incident where the suspect has gone, or the crime is threats over a phone - the priority is lowered.
Mix into this pot all other jobs that the police deal with. People threatening suicide, people phoning to say they have taken a load of tablets, missing kids, sudden deaths etc etc. These take hours & hours to deal with as there is no one else to deal with them and a suicidal person can't just be 'fixed' in minutes.
Add to this custody wait times with prisoners often stretching to 3 hours before you can book them in. Then having to take the prisoners to hospital if there is the slightest thing wrong with them and guarding them there at the back of the queue in hospital, or cell watching them because they have threatened to bang their head off the wall.
And also remember that each officer carries about 20+ crime enquiries on their queue with each victim wanting their job to be a priority, CPS wanting a full case file before making a decision on any of those enquiries, case files taking days to complete due to all the Body Worn Videos now having to be transcribed & redacted by the officer (no admin staff to do it for you).
Then you have a boat load of other jobs constantly coming at you.......
I could go on - but this is why sometimes you might have to wait