Bead is where probably 99% of all slow leaks originate. It's the most susceptable area, with regard to dirt, scratches, or debris. A slight deformation isn't a problem, tire will conform to it, but a scratch or sharp dent will usually require bead sealer to seal up.
Those bicycles have tubed tires, whereas I thought your tractor tire was tubeless, so a whole different kind of valve stem. Personally, I've only ever had one stem failure in nearly 50 years of working on tubeless tires running standard OEM stems. I really wouldn't worry about it, unless you're subjecting this tractor to conditions where the stems is likely to be torn out.
The metal screw in types have their own issues, in that they have no flex or give, and are more likely to break or damage your rim if you do hit something with them.
If bead area leaks, which you can find with soapy water, then pop the tire off the bead, clean everything, and see if you can find any damage causing the leak. If there's damage causing the leak, bead sealer would be the thing to try first. Slime is not the best product for that, IMO.