I know that some people do this because of poor eyesight or arthritic fingers or something similar, but for the rest of us clipping a fly onto a snap is nothing more than a crutch.
The ability to tie good knots is an important skill needed in fly fishing and one of the easiest to master.
When you have free time like when you're watching TV, have a spool of mono there and practice. It doesn't take much to get a good grasp on the essentials.
It will be worth it.
The simpler the outfit, the more skill it takes to manage it, and the more pleasure one gets in his achievements.” --- Horace Kephart