Somebody needs an hour today. Behind a search about leaving a child for a short while there is an appointment, a deadline or a parent who has simply run out. Nothing else on the site speaks to that state.
Holidays concentrate everything. School breaks send parents looking for anything that fills a morning, and a centre with holiday sessions published in advance captures weeks of demand in a few days of searching.
Workshops get looked up by what happens inside them. A parent choosing between a Saturday morning of baking and one of painting types the activity, never the venue, so naming each one catches families who had no intention of visiting a play centre.
Age is the filter that decides. Whether a two-year-old can be left, and whether a nine-year-old would be bored, is checked before anything else, so stating the range clearly saves everybody a wasted journey.