I'll let you in on a little secret. While one reason for lockdown is to give the egg a stable hatching environment, it's primary purpose is to keep whoever is incubating the egg from messing with it too much.
You've observed that letting the egg hatch in one's hand does no harm to the chick if you know when it's ready to hatch. Stick to lockdown for your first hatch. But as you get more experience you can trust your judgment about how to approach individual eggs. If a chick is clearly not having any trouble you can let it hatch in your hand or even let it hatch in the brooder if you want to create more space in the incubator.
You'll see people telling you that 100F and 75% humidity are "optimal". But, even if that's true, your chicks don't need optimal conditions to hatch. You can get decent hatch rates with a still air incubator or a broody hen, and neither are high precision instruments, never mind optimal.
You'll also hear stories about shrink wrapped chicks, hatchlings bleeding to death, or other problems. You shouldn't ignore those possibilities. But the problems need to have certain conditions met to occur too. You're unlikely to shrink wrap every chick in the incubator if you open it to remove an egg. Similarly, if the chick pips in the wrong place and you enlarge the airhole he's less likely to bleed to death than he was to suffocate.
It's okay to break some of the rules sometimes. But first you need to learn what the rules are and why they exist. It's better if your learning is the result of research, planning, and forethought though instead of trial and error.