@alavapenguin: You could justify it by taking the grassroots history of wrestling. House shows, much smaller than WWE productions take place in high school gyms and public centers. They throw extra chairs not being used by staff or punters under the ring because they don't have anywhere else to put them. Same for tables.
Other than that, for a while it sort of became a thing that wrestlers would place the items under there for later use, like HHH would place a sledge hammer under the ring before the show starts so he could use it.