What other kinds of items are relatively soft and small? Snack cakes? Socks? A hat maybe? There aren't that many, and some aren't very practical to throw on the ice. Plushies fly through the air relatively well, won't hurt if they accidentally hit someone, and are relatively safe to throw on the ice. Flowers are a huge hazards. If someone throws a bouquet and it hits another audience member or skater wrong, it could poke their eye. They are also heavy (all the water content), and fragile, which means a potential hazardous mess on the ice.

I think part of the reason people throw plushies is just because it's fun. When I went to Nationals a few years ago, I bought some cheap ones at Target and they were fun to throw. I figured they'd probably get donated, which is fine with me, since that's a good cause. I didn't see them as a "gift" to the skater. And some men do like plushies. My husband is 30 and we have a plushie wall in his home office. Granted, some of these are "collectibles" he got from work (tech industry, so they get some quirky things).