Xero has a partner program that gives some benefits to signing up clients. You'll find the details here: https://www.xero.com/au/partners/partner-program-table/
MYOB has a similar partner program where if you sign a client up, instead of them paying the retail price, they can pay a discounted price OR you can get them to pay retail and keep the difference.
Reckon also has a partner program.
So all major software developers provide some sort of incentive to push their product. It's our firms policy that we don't recommend a single option over another to any client - but to present the client with the information on all suitable options and let them make the decision.
The thing is, Xero wins out in just about every situation. As /u/MakeMitchRich has said, Xero is just so much easier for us to deal with. Quickbooks has recently launched a fully online package that is substantially cheaper than Xero and has some good features, but it is missing too many necessary features for me to recommend it yet. I can see it being great one day though.
Xero gives us far better control, we can access the client file at any time to assist them, we don't have to worry about backups and versions, the user interface is far more user friendly than any MYOB desktop version and even more so for any Quickbooks/Reckon Accounts desktop package.
Xero really reinforces the need to do proper bank recs, where as I've had clients give me MYOB or Quickbooks files that haven't been reconciled in years. They just become an unusable mess.
I'd be interested to know what the client you are referencing to is doing that you think it wouldn't be suitable for Xero. Xero has so many additional plugins that I'm yet to really find a situation it wouldn't work in.