There are a lot of operators that accept the SPT Zonecard but not the Daytripper.
http://www.spt.co.uk/travelcards/zonecard/
Obviously McGills are the biggest and most inconvenient one to be excluded but there is a substantial number of operators on that list.
Judging by the link you posted, if the service is SPT-funded they'll accept it, if the service is commercial they won't.
The vast majority are commercial with only a small number of infrequent routes and odd off-peak services on otherwise commercial routes SPT supported.
Yeah its an oddity, to be honest they probably want the money directly from the paying public...
Most operators really want people on their own day/week/month tickets, not only to get the revenue but to keep it out of their competitors, however that would be more relevant to commuters or day return users. The likelihood is that anyone wanting a daytripper will buy it anyway and they will actively avoid non-participating operators, I find it hard to imagine there is any net revenue gain from not being included.
Obviously the revenue from the commuter tickets is too much for the operators to turn down, whether the lack of parity on the datripper is down to the operators wanting a bigger cut or SPT just not actively keeping the product updated is the question.
A policy that to be included in Zonecard bus companies must also accept other multi-operator tickets would seem to be the most logical, however it has always seemed to me that SPT is one of the poorer PTEs when it comes to regulating and promoting the bus services in their region.
It is all the more disappointing considering Arriva accepted the ticket so validity has been reduced significantly with their routes going to McGills (not accompanied by a reduction in the ticket price I'm sure). Also you have to wonder that if Stagecoach are getting enough revenue to allow it on their network of express services why more local operators cannot accept it?
