What is the benefit of putting things in storage?

Storage is unlimited, so you can keep putting things in there, like past seasonal sets. It helps if you want to redecorate your island or move many items at a time. If you are running out of space, you can put some items in storage and replace them with high-flower items. When you need to level up, you can take things out of storage to give you the flowers you need right away (instead of buying a decoration and having to wait for construction).