I would suggest passing them on to a neighborhood kid versus throwing them away. Introduce new modelers into the hobby.
Or if you wanted to make some money, put together an "as is" lot of started models and sell them on eBay. You might make $20-50 depending on the kits. There is some modeler who can't afford the price a new kits, but would jump at the chance to get a handful of partially assembled kits at an affordable price.
And some modelers like to customize or scratchbuild different variants. Getting bits and pieces of kits at a discounted price that you need to make the variant you want to helps.
My oldest unfinished kit is a Tamiya M2 Bradley that I started towards the end of my college days in 1986. It stayed in my parents' home in Vermont when I left for active duty. When I moved to Fort Devens, Massachusetts in 2001, it was still there, unknown to me.
My parents were downsizing and becoming snowbirds, moving to Florida in the winter and returning to Vermont in the summer. So, in 2004, they asked if I wanted any of my old stuff. I found some of my old, completed model kits that were stuffed in kit boxes.
Some of those ancient kits that I built as a kid had a lot of sentimental value to me. There was an AMT VW Rabbit that was a model of the very first brand new car I bought in 1984 (it's an earlier model). Another kit was a very old Monogram M48A2 that I built in junior high school and later, after I became a tanker, painted it to look like an M48A5 I trained on in 1985.
They represent a snapshot of my model building nearly 40 years ago. While I've been tempted to finish the M2 Bradley, I doubt I ever will. I know I'll never part with it.