What do the NES-101, SNS-101 and the Sega Genesis model 3 all have in common? The sheer lack of a power LED. Does this fact bother me? Not in the slightest, but for some reason a lot of people can't live without a power light on their console.
If you want a power light on your console just because you like to have one, that's fine. What really sets off my bullshit alarm is when almost every person I've seen doing a tutorial on how to install a power light gives the excuse "Without a power light I don't know if the console is even on.". This excuse was also used by someone giving a review on the NES-101, where their main complaint about the console was just that.
Let's be honest here, if you're playing a video game there is absolutely no doubt that your console is on. Once you've finished playing that game, or any series of games you wish to play, the console is shut off. This is a fairly common practice and doesn't require any console to have a power light for you to know whether or not the console is powered on or off.
What if you need to step away for a few minutes and have a snack, eat a meal or perhaps you need to leave the house for a few hours and run some errands? Then maybe, in the name of safety, you should shut the console off anyway. But you're playing a game with no passwords, no save points and it has taken you a long time to get where you're at? If you're that committed to beating the game how could you forget the console is on in the first place? Wouldn't you be excited to accomplish this feat, therefore causing you to get your chores and tasks done so that you could finish the game? You shouldn't need a power light to tell you the game is still running and needs to be finished.
The only time I've wished a console had a power light was when I tested consoles that I wasn't sure were functional or not. A power light would give me a better idea whether or not the console is getting power. But the reality is that since I was merely testing the console to see if it worked or not a power light isn't even needed. If you're testing consoles that may or may not work, you are most likely going to try to repair them, in which case it is solid advise to go find a decent multimeter and check that way.
Regardless of your personal need for a power light, the whole "I can't tell if the console is on" is a totally bogus excuse for adding one to a console. I'm not opposed to modding consoles for your own personal tastes, needs or desires, far from it. But to join a bandwagon of people using the same lame excuse is in and of itself pretty stupid.