I'm not so sure the OP is bent on doing it their way versus what you're recommending. It's just a matter of them wanting to know WHY you're recommending what you are versus what they're asking about.
To the OP: It will be good for you to read the
Wiki and the
Cliff Notes, etc., and it's good to ask questions as you are, too. Just realize that most of this has been asked and answered thousands of times before, so some get tired of going over the same ground repeatedly. What seems like innocent questioning (and I believe it is) can seem like argument to someone like fenderman who has explained this many times, I'm sure!
Most of the cameras have apps and such, and are set up to do just what you want, at least to provide alerts, emails, etc., without needing an NVR or
Blue Iris, etc.
But while they're easy to set up to do this, there are usually serious drawbacks to these fast, easy, inexpensive implementations. I've been there!
So what fenderman is pointing out is that without something more sophisticated in "the loop", like Blue Iris, for example, things can be cumbersome to get to do exactly what you want. And he's pointing out that you will likely want a fast, easy, convenient way to switch the messaging/texting/emails/alerts on and off, and perhaps have even finer control so you can enable and disable different alerts, etc., easily and really tune the system to your needs and be able to make changes easily, too. And that's where Blue Iris really shines.
It has so much capability when it comes to configuring groups of cameras, schedules for everything, and fast ways to switch modes to suit times when you're home, or just in the back yard, or out and about, or at work, etc., and have that all tie in with time of day, light conditions, whatever. Most of this won't occur to you when considering setting up a few cameras at first. But as you play with it and live with it for a while, you'll almost certainly come to wish you had better control over things. So like fenderman says, you can try it out the way you're proposing, and then as you run into things you don't like, you will likely find yourself wishing for more, better, and more convenient control over the behavior of the system. Really, that's how a lot of us have come to end up with Blue Iris. We've tried it the way the camera manufacturers provide, which is easy, cheap, and works. But then we've run into the limitations or hazards of those setups and opted for something better.
I think fenderman is just trying to move you past making some of the mistakes and get you directly into doing things right the first time. But I'm not even sure that's always possible. Lots of times we do have to play with things to learn enough to even know the right questions to ask. And that brings me to another point. I think you'll find that you get amazingly detailed answers from a lot of the folks here - answers that take them a long time and a lot of effort to formulate and then post in a painstaking way - when you ask questions that are sort of "deeper into" the whole subject. Those questions are the ones people find to be more "worthy" and more interesting, so they tend to put a lot of effort into figuring them out and explaining them.
So don't be put off. Do try to read the Wiki and Cliff Notes, and scan through some of the existing threads here, and take your time. There is, (unfortunately) a LOT to learn about all of this.
To make a system that is secure and doesn't expose your network to outside attack, works well, and provides the type of remote access you want, etc., is very possible. But unfortunately, while the cameras themselves can "sort of" do a lot of what you think you want at first, in the end, most people end up not satisfied. And just what fenderman is talking about with regard to being able to easily switch off alerts, or change things easily is one of the things may well make you unhappy very soon after setting things up. Another big problem most of us have is securing our networks while still allowing for alerts and remote access.
Still, if you get a camera and play with it in its most basic and simple modes, you'll gain some feel for all of this, so that's not necessarily an entirely bad thing or a big waste of time. Just don't expect to be completely satisfied, and don't buy a whole bunch of cameras, etc., until you've learned a bit more. Unfortunately, setting up a "perfect" security camera system is not something that can be done really fast and easy. Most of us have ended up putting a lot more into all of this than we ever figured we would when we first started.