These were designed to be non-refundable tax credits that would reduce the tax burden on the amounts spent for these activities. If there's no tax burden on the amount spent--you don't have the tax payable to absorb the credit--making them refundable would not serve the purpose of reducing any tax on that amount, because there's no tax payable.
Evidence of meeting #24 for Finance in the 41st Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was infrastructure.
A recording is available from Parliament.