Short answer: Everything is negotiable and up to each individual agent.
The more nuanced, and lengthy answer is below :
Based on your questions you're indicating to me that you believe you know as much or more than I do about real estate marketing and don't value my experience. I'm not your average agent, I'm in the top 5% of all agents in terms of successfully closed transactions a year. I spend more money marketing my listings and my business in a year than the average Realtor earns before taxes in a year as well as money for professional staging consultations for my sellers, appraisers to draw up accurate floor plans for my marketing, professional photographers, house cleaning once you've left, home warranties for the buyer to remove any objections etc. I don't sell 100% of my listings, but i do sell 90+% and they tend to sell in 120 days or less because of my experience, advanced marketing techniques and negotiating skills. My time is valuable and it's all I can really control. I don't waste it and have long ago learned my pragmatic, realistic approach doesn't resonate with all sellers. That's fine, I don't need every seller. Now given that most full time agents take home less than $25,000 a year and are living from pay check to pay check it's easy enough to find an agent who will take just about any listing their offered under the most ridiculous of terms. Weak agents are happy to give away money, it's really about all they have to offer someone in order to get them to work with them. Savvy sellers should be asking themselves," If this agent is so ready to give away their own money, how hard will they fight for my money.?"
I also don't waste my time with buyers who think they know more than I do about my market place. Honestly I've never met one that knows half of what I know, but I've met plenty who think they do, which is their prerogative. My prerogative is to chose who I'll spend my time with.