Marketing. I would take everything on this website with a grain of salt. Take it from someone who has actually built an off-grid system, one that is relied upon for 24/7/365 living rather than mere vacation cottage. For example: OP re lead-acid battery options: "Heavy, cheap, easy to use and they work! Typically will last about 3-5 years. Slower charge rates than lithium, much heavier, and they cost way more in the l…
I actually do see this all of the time. In decades of owning multiple cars I've found the batteries tend to fail so regularly at about the 5 year mark that you could set a watch to it.
They are easy to find and inexpensive to replace, but they absolutely do have a limited lifespan.