I think you’ll find that many store cards are really Visa or Mastercard.
Many Canadian store cards used to be owned by the stores. Some of the department store ones were very profitable.
However, many firms ‘rationalized’ by getting out of what was seen as a financial services business line to focus on their core retail. Weston’s with PC Financial is an exception - but for many consumers there are other reasons not to go with Loblaws/PC branded financial products.