Why cant Debit or Interact online be included as payment options?

I assume you mean Interac Online (no "t"). It isn't included because honestly I've never heard of it before? That doesn't rule out our adding support, just that we would need to justify the implementation time with a major advantage.

You should be able to use any Visa or Mastercard labeled Debit card with our existing payment gateway.

[EDIT] As far as I can tell, Interac is a regional payment system in Canada, with support from a few dozen banks and credit unions. I think that's cool and all (I use a small credit union), but we would probably need a much larger potential customer base to justify the development effort of integrating support for them.

Lastr I checked you can use your Interac account through PayPal as a bank transfer. Why not use that?