First of all, happy birthday
In regards to the topic, personally, since this is a forum, i fully expect people to want to ask for opinions like that (one reason or another) and i'm fine with it as long as it doesn't break any forum rules (to be honest, i, myself don't remember all the details). I don't think there's that many that it overwhelms the forum thread overall discussions.
Still, i get what you mean. Though on the other hand, i can understand why those authors would want to test the water, seek validation, or maybe promote their novel as well. Most likely, it's because they don't have anyone irl to help give them opinions, validations, and or critics. Since this is a forum where authors gather, they don't think there's anything wrong in asking such things.
But I do like SHF that discusses many other things in comparison to other writing forums and i don't want that to change.
My advise for those author:
Rather than asking something vague about whether or not someone will be interested in a story premise, try to write it first, publish a couple of chapters, and jump into feedback threads (or tempokai's roast thread if you have a steel, fearless heart). You can also make a thread asking what you can improve, whether or not you're bringing the plot to an interesting direction, and anything else you need improvement with. You can even review/feedback swap with other authors who shares your interest to get one.
You can't do any of that without a story to begin with.
Your writing itself is more important than the idea and do have fun. If you got stuck on worrying whether or not the idea will sell/popular, it'll only be a stone dam for your ideas.
Thank you for coming to the ted talk of someone who has a lot of free time in their hands