Giving a poor person a vintage 68K mac as their main machine is about the same as throwing it away. There are tons of much newer and usable machines they could get for free or close to it and get work done.
The way I see it saving a machine from recycling is not permanent. Somewhere along the line the next owner will either like to mess with it, be able to pass it on to another collector, or will recycle it. The best machines of the time that still exist will end up with collectors (if there are any), a few of roadapples will be around because of rarity (most will have been recycled). There has to be a want or need for the old gear or it will end up recycled today or 10 years down the road. Don't worry about just preserving items for other generations, trust me if they want it they will find it or make a new one.
The way I see it saving a machine from recycling is not permanent. Somewhere along the line the next owner will either like to mess with it, be able to pass it on to another collector, or will recycle it. The best machines of the time that still exist will end up with collectors (if there are any), a few of roadapples will be around because of rarity (most will have been recycled). There has to be a want or need for the old gear or it will end up recycled today or 10 years down the road. Don't worry about just preserving items for other generations, trust me if they want it they will find it or make a new one.