Actually, I understand the theory behind eBay favouring newly listed items.

Now that there are so many business sellers on site with GTC listings that have been running for years, it's probably their way of trying to maintain fresh content in search results so that theoretically (if not actually), people see new and different items rather than the same ones all the time.

The theory is sound, but it neglects to truly take into account how diversity is achieved and why people like it.