One reason is the “almost free lunch” that solar offers after the initial cost–but I believe I've stumbled on a second reason, one that I've suspected but had no proof of.
I'm reading a fascinating article. It has information that should swing folks who are weekend warriors to solar! Here is a quote (note the second sentence!):
“In order for the data to be of any use, the readings must be taken while the cells are in a float-stabilized condition. Float stabilization can take weeks to months to accomplish.”
The whole article is here:
The float stabilization which solar can offer may be what is producing long term battery life. The same may be true for long term shore power use with a top of the line 3 stage converter.
This suggests to me that discrete 2 volt cells may be the best ultimate choice, if the pocket book is deep enough.