Hmmh, this, like many decisions/issues facing a kilt wearer is very much a personal decision. Someone suggested that wearing a sporran insured that other people knew you were wearing a kilt and not a skirt. I would suggest that if they know that a sporran is typically worn with a kilt, they already recognize what you are wearing as a kilt, and if not, the sporran won't make any difference.

I will often head out of the house without a sporran, although I always (I think) wear a belt. Lets run through what I carry in that situation. I have to have a wallet (ID, money, family pictures, etc.), cell phone, and I have to have my car keys. That is a bare minimum for leaving the house, even when I am taking my morning bike ride!

So, if I don't wear a sporran, how does it work out? Well, cell phone clipped to the belt or kilt waistband, keys (I have a remote door opener) shoved into the belt/waistband next to the cell phone, and the wallet (a standard single fold type), is placed on the belt/waistband at the small of my back. It fits perfectly, will not get lost, and nobody will consider taking it away!

Just my approach. You can also stitch a small square of fabric to the underapron and make a holster for your wallet, keys, etc..