If you are a new seller, eBay have none of your selling history, so they need to see that a paid for item, will be shipped and delivered to the buyer. If you have tracking showing delivery, this will speed up that payout, and it is sent to your bank usually within a few days.
This has to be in place otherwise anyone could come on eBay sell expensive items, take the money and not post out the item. Once you are established as a good seller posting out items promptly, this hold stops, and you can select a daily or weekly payout from your sales.
If you are a returning seller, that is, you have returned to sell after a little break, then sudden selling activity raises red flags to eBay as some dormant accounts can be hijacked, so eBay wish to see that the genuine seller has returned.
Here again, tracking showing delivery will release the money sooner, as eBay as happy the genuine seller has returned to their account to sell again.
