not sure how many transactions you do but without a store you cant search your listinsg or sold items so say for example someone messages you and asks you about somethign you have to go line item by line item looking where with a store you can search something from the title and pull up the listing right away.
$15 isnt' a crazy amount i mean one sale a month should be able to cover that. ebay wont admit it but i feel like you get better search ranking with a store as well
What? I only list about 10 to 20 items a month (but there are always that many on there as things sell) and if someone sends me a question about an item there is a notice at the top of my homepage saying I have an unanswered question and the link takes me right to the item. Even if I had 100 items that would be the case. No store needed for that feature.
They promote that one gets a better search ranking, but I have listed an item, signed out, just went into eBay without signing in and did a search for the item I just listed or maybe one I listed a day or two before. Invariably my item will show up in the top five listings. No store association.
This January, 2014 I will have been selling for 10 years on eBay and I never really saw the need for a store. There may be some other reasons I don't know about, but in this case ignorance is bliss.