I throw out tubes that have a hole and I've taken off the bike. For the following reasons:
1. Flat Resistant Tires - have meant that I hardly do much patching any more
2. Cost - you only save $4.50. $9 for a new tube vs $4.30 for a patch kit, that's not paying for your extra time
3. Glue Patch Kits are 1-time-use - in my experience the glue tube glues itself shut not to long after using it the first time and can never be used again

I've seen arguments that you can buy stuff to patch your tires in bulk much more cheaply, and have glue that doesn't glue itself shut, but at less than 1 flat a year on average it's not worth the extra storage space or hassle for me either.

I fix my own flats party because the time and inconvenience it would take me to take it to and from the bike shop is greater than the time it takes me to do it myself. I also like being able to do it if I get a flat while riding. But I just don't see a cost benefit to patching tubes when I so rarely get flats. I think it's simply cheaper to put a new tube in and throw the old one out.

This might not apply to everyone. The equation is different if you're retired on a fixed income or savings. It's different if you live somewhere where you're getting a lot more flats than I am. But for me, I feel it's more costly to patch my tubes than it is to put on a new one and throw out the old one.