Also they get to choose which charity gets the money, so that can be a way for upper management to trade favors with other people in upper management on the charity or its board or, even worse, to actually put money on specific people's hands - I keenly remember when it came out that the way the IKEA owner evaded taxes in Switzerland was a convoluted ownership structure that ended up paying dividends to a registered charity in Luxembourg whose stated purposed was "The advance of interior decoration arts" and which paid for all the expenses of said IKEA owner.

Point is, there are a lot of fishing yet entirely legal things that can be done with the customer's charitable donations when a company controls which charities get it, especially since the criteria for something to be a registered Charity in certain legal jurisdictions (most notably Luxembourg and pretty much all British Crown Territories) are incredibly weak.

If you want to give money to Charity, chose yourself which and do it after at least some due diligence to filter out the ones which aren't actually using most of the money on their stated charitable objectives.