This is the lite version, so yes, it does not have every feature available for free, and we’re very clear about that on the info page. Yet we still have hundreds of users that use the lite version to keep track of internal stock that doesn’t affect frontend product availability. Just because it’s not useful to you doesn’t mean it’s not useful to anyone else.
I am one person developing, maintaining, and offering support 7 days a week. For the full version I’m not charging an arm and a leg like some other premium plugins. It’s $29 once-off for lifetime updates, of which I get $16.
If you don’t think a developer’s time and effort is worth anything, I don’t really know what to say. Perhaps you’d prefer 100% free plugins that the developer gets bored of and abandons after a few months?