It is not usually essential it is just the checks you carry out . Most training aircraft are a gazzillion years old and the checklists are tried and tested .
If you are in a position to be joining base leg , firstly your checks should have been completed already .
You are not going to be asked to turn base leg until the very earliest end of the DW leg anyway so checks done .
Your priority is always to fly the aircraft at every stage of flight not just the final portion , your checks are part and parcel of that flight .
The checks are there for you to follow , if you deem them not essential then that is up to you but eons of aviators and manufacturers have done so . Follow the checklist for your aircraft it is there for a reason .
Brakes (not just check pressure check they are off ) yes it does happen
Undercarriage , it may be fixed , but one day you might fly an aircraft that it isnt , good early habits stop bad ones developing
Mixture (obvious I hope)
Fuel ( dont just think about running out think about changing tanks if necessary) a few aircraft have had a bad day due to fuel starvation on take off and landing when the other tank was full (people miss changing tanks on freda too)
Flaps you may be playing with them on final approach but you can also lower them early too you may want a slower approach speed earlier , many many reasons why you might want flaps early. You may also want to check they are up , many a person has been GH with flaps down and forgotten about them , turn base leg , first stage ,,oops full flap
Carb Heat you may fly an aircraft without it , then all of a sudden you go back will you remember ??????
Hatches again obvious
Harnesses, perhaps like me you are a bit fat and loosen seatbelt in flight , downwind you can tighten it up again if necessary
.
There are many other reasons for these Im sure someone will come up with more .
If you only ever intend to fly a 152 then fine you do what you feel is right
But everything in avaition is done for a reason , well most things
Why would you be UNEXPECTADLY be asked to join anywhere you should or would know in plenty of time , never assume