I'm a Guide Leader (Guides are the UK equivalent of Girl Scouts), and although we don't sell cookies, we do take part in various other fund raising events.
A few years ago, I experienced JW disapproval of Girlguiding, which shocked me at the time.
My first post on this forum was to ask JWN members for advice on whether a young friend who was studying with the JWs would be allowed to continue her training to be a Brownie Leader if she joined the religion. (Brownies are younger Guides).
I was told by forum posters that there would definitely be a conflict for my friend between being a JW and doing weekly voluntary work with the Brownies.
However, when I told her about this, she was incredulous and confidently asked her Study Conductor to confirm it was not true. She came back to me triumphantly to say she had been told that if she wished, she could continue as a Brownie Leader but just had to avoid being involved with Easter crafts, Christmas celebrations, singing Happy Birthday, etc and should not make the traditional Guiding salute to the UK Flag. She was happy with this and didn't see any problem.
This was during the 'love bombing' phase. However sure enough, as JWN members predicted, after a short while, she was told she should consider how working with the Brownies was affecting her relationship with Jehovah. There was a lot of guilt and pressure until sadly and reluctantly she resigned from Guiding.
She ended up in misery and deep depression as she was being controlled more and more tightly. Long story short, eventually she was 'rescued' from the Watch Tower Org, and immediately and happily rejoined her Brownie Unit.
I had never been a JW and before this, had not known much about them. As an outsider, it showed me that the JWs were a harmful cult, rather than the slightly crazy but well-meaning group I had previously believed them to be.
So I guess that in the same way, in the USA, Canada, Australia, NZ etc where selling Girl Scout / Girlguide Cookies is common, a JW refusing to buy or eat one would give them 'bad' publicity in the eyes of worldly people .
Incidentally, in the UK, last year the 'Promise' that all Guiding members make was changed to take 'God' out of it completely, and Guiding is slowly heading towards becoming a completely secular organisation. But it wont make any difference to the JWs I guess.