I can see the micro-aspect as most of these target niche markets, are run by solo-founders, etc., but what differentiates these from traditional small businesses other than the fact they sell digital products and services?
Exactly. The most significant differentiation is that most of the tech projects run worldwide. The founder might not have a permanent place like other small traditional businesses. You could be a nomad with a desktop and Wi-Fi in Bali and travel without being fully dedicated to the business. So, for me, it's freedom.
Sometimes people just don't have enough marketing skills or don't want to promote products but they might have a great potential to make a revenue. In this case, you're right, focus on profit is a great to have to attract buyers.