Not all helmets are created the same. I don't think the typical bike helmet is very effective is preventing I injuries where the skater falls backwards which is typically the type of bad falls I see. Maybe a ski helmet would be better but most families don't have those.
The helmets that are recommended are those designed for use for hockey, skiing, skateboarding, scootering...
Then as the children progress the next step is often a Crashe, Ice Halo, or RibCap padded hat/padded headband.
The USFSA does recommend specific types of helmets for Learn to Skate and to their credit their brochures about Learn to Skate programs show many photos of kids wearing helmets. It would be good if ALL the photos of beginner skaters were in helmets. And it would be good to see young figure skaters wearing padded head protection too.
https://www.learntoskateusa.com/