Because people in their LAP travel to Brisbane and therefore might still be interested in those businesses. The same as how a Bendigo business might choose to advertise in Shepparton, or the Gold Coast theme parks advertise in Melbourne.
These bordering regional stations don’t become de facto metro stations by being able to advertise metro businesses. The damage is done by signal overlaps that are either poorly planned and/or cannot be controlled. Will you also force people in metro areas to only listen to metro stations? Arrest someone in Brisbane listening to River?
It’s hardly unfair to the metro incumbents too - they advertise regional businesses from time to time too. If anything, a regional station being full of metro ads hurts the local regional businesses who get priced out of advertising on their local station.
Don’t be ridiculous. Preventing operators from adjacent markets being included in Metro ratings is completely different than not allowing people to listen to them if they can receive them in adjacent markets.
The signal overlaps can’t be helped but the ratings can.
There’s a grey area where some oprerators will advertise holidays interstate and in different markets, but having River 949 for example in the Brisbane ratings would mean they would likely advertise more businesses in Brisbane than Ipswich, which would be detrimental to the Brisbane broadcasters and it may prompt ACMA into action.
When those types of restrictions happen (elsewhere), usually the agreement is to not solicit advertising outside your licence area. Note “solicit”; if 96.1 were in that situation, and someone came to them and asked to advertise, there’d be nothing stopping them accepting them. And why would you not when we’ve known for decades that 96.1 blankets so much of Sydney so well.
Something like a C91.3 is a harder sell for Sydney ratings. Most of the population in Campbelltown RA1 (essentially Campbelltown LGA and the main populated parts of Camden) overlaps with Sydney and those numbers may be useful, but it wouldn’t be the whole story. WIN has wanted it to be seen as a whole-of-Macarthur station (especially after they woke up from the “C is for Campbelltown” phase which may have alienated some of its audience), and practically all of Wollondilly Shire is outside that overlap. Somewhere like Picton would have traditionally struggled to get Sydney FM in parts apart from the WSFM retransmitter on Mt Razorback, and southern parts of Wollondilly would possibly even be competing with the highlands version of 2ST/Power FM.
That sort of setup means I wouldn’t be surprised if they preferred the regional model (provided by Xtra Research), which WIN is already used to in Wollongong. Although they don’t even release AQH-based ratings, merely a “station listened to most” figure, and maybe that’s all they need in such a market.