Why do LLs...

[mariner]

offer fixed term ASTs, with/out 6 month break clauses, in excess of 6 months?
Examples:
LL cannot prevent T having water meter fitted if Tenancy >6 months
Many break clauses seem to allow notice any time after break clause date.

[mind the gap]

offer fixed term ASTs, with/out 6 month break clauses, in excess of 6 months?
Examples:
LL cannot prevent T having water meter fitted if Tenancy >6 months
Many break clauses seem to allow notice any time after break clause date.

LLs offer fixed term ASTs in excess of six months because (generally speaking) many tenants do not want to have to move house every six months and it gives them a little more security of tenure whilst a break clause offers both LL and T some flexibility. In a market where there is an excess of rental property, it may give the LL an edge; it also means the LL does not have to go to all the upheaval of finding (or paying an agent to find) new Ts twice a year.

You give the impression that all Ts will change the meter and behave badly, where most do not. In an ideal world, LLs would probably prefer to keep the same Ts indefinitely. It's a lot less trouble.