Why? Well, in rare cases, it may break and someone could ingest it. No, I have never heard of it happening, but better to be safe even if you provide good instructions on how to disassemble a cake before serving.
What are the options?
#1 - Use a coffee stir stick to house all the wires. This bowling cake has a starburst of many wires. This monkey cake also shows the stir stick which makes it easy to disassemble before serving.
#2 - Wrap your wires with floral tape. However, most floral tape have latex in it and you have to watch for latex allergies. Have I ever heard of any allergic reactions? No, but its better to be careful and inform the client.
#3 - Use Floral Spikes. These are usually used for fresh flowers, but I use this for sugarpaste flowers. They are expensive, but worth it. For this cake, they were easier to remove and preserve as the sugarpaste petals didn't touch the cake.
#4 - Dip in white chocolate or white candy melts. If none of the above options works for your design, you can also dip the wire ends with white chocolate or white candy melts.
I hope you find these options helpful. Again, it is rare that there are any issues, but I do this to be on the safe side. Anybody do anything different?