It's because that's what the game is. It's difficult, uncompromising, and you have to meet it on its terms. I concede that at this stage, a lot of the invasions you will get are people who have done an SL1 run or at the very least know how to become powerful at a low level, and that is an unfortunate side-effect of the system. Furthermore, a lot of the invaders are people who know their way around, and have already defeated the Four Kings and joined the Darkwraiths, meaning that early on invaders are almost inherently powerful. The game does give you four Cracked Red Eye Orbs right at the beginning to encourage PvP at a low level and at low progression through the game, but the reality is people want to give themselves an advantage, and I don't blame them for that considering it costs them a humanity to invade.
Look...I like the mechanic, and part of the game is this unexpected invasion. It only occurs when you're human because you can summon help as easily as you can be invaded. Unfortunately, I'm also against the ability to opt out because one, you're not playing the game as it was intended, and two, you're limiting the pool of people who can be invaded. I think if you're going to summon white phantoms you take the chance of being invaded, simple as that.
I have a solution for you though. Join the Way of White covenant. It's the first one in the game, through Petrus, so most new players take advantage of it without even knowing, but the effect is if someone is invaded, Way of White members will only be invaded if there are no players of other covenants available. You're essentially last on the list for invaders. Furthermore, it improves your ability to summon other Way of White members, Sunbros and Princess Guards, so it's basically ideal for you. It's virtually useless for all other intents and purposes.
Furthermore, a necessary evil in my eyes that circumvents a mechanic of the game for practical reasons but anyway, you have a Black Seperation Crystal that will send home any phantoms you want allowing you to get rid of invaders as soon as they turn up. Use it if you must.
tl;dr: The worst kind of terrible person.