Coops should scrap charitable donations and instead invest the money into new coops. Charity tackles symptoms, coops change structural root causes.
It would have a deeper, more sustainable social impact, improve the bottom line and distinguish coops more from capitalist firms.
Right now the charitable work coops do is indistinguishable from that of their capitalist competitors, at least to the ordinary member.
Would put it this way - most co-ops are grassroots organisations, but the co-op sector as a whole is dominated by big giants, in the US entities like the Dairy Farmers Of America, ACE Hardware, credit unions, etc.
The SME co-op sector generally does a great job in supporting the movement, the big ones do a bad job.
Often co-ops do come together and merge into bigger co-ops, iirc Dairy Farmers Of America for example was a result of merging three dairy co-ops.
In terms of communication and public image there probably would have been some advantages as you point out - although there might also be some advantages in having a unified brand.
Would guess that the merger probably reduced costs - instead of having three boards of directors, you only need one, instead of each of them doing the bureaucratic work to abide by regulations separately, they only need to do it for the one entity, etc.
A Fediverse instance for people interested in cooperative and collective projects.