Trimmers and chain saws operate in different positions, sideways, upside down, etc. Boats and snowmobiles aren't (usually), so an oil reservoir works on those, but not on the others.
I'm thinking of switching to rechargeable yard tools. I'm getting tired of having different mixes and dealing with all that not starting/running crap having to clean out carbs/replace parts/etc with my trimmer, blower, and chain saws.
My mowers are OK. My 2005 John Deere riding mower runs great and has never had any problems.