The issue I have with conferences like Sony's and Microsoft's is the length. Sure, there's a lot to talk about, but usually, the "meh" or dull moments usually take longer than the more hype moments. I was impressed by what Sony showed last year, but they still had moments where I was like "...okay...." Like I don't need to hear the next Madden or something when we kinda expect them to be mostly the same, with a few tweaks. Though the moments of awkward claps can be a bit hilarious because even I wouldn't know how to react to certain announcements that have that kind of reception.
Plus, we're in an age where the Internet is huge and almost everyone has access to it. Nintendo's directs or digital events are effective because that's were most of the audience is going to watch nowadays. Sure, they can spend a little more money to create a big press conference and have a live reception, but if that's what they want, that's what they want. Of course the main issue is the potential lag, but even then, live streamed conferences can also potentially lag.