Of course it happens in iPhones and ALL laptops and phones in some small number. Defects will happen; and most of the articles you point to are again user damage (the student admitted the phone had a crack meaning could've had unknown internal damage causing the battery to rupture, and there is some hint it was in his back pocket meaning sat on it) and the 7 that blew up during shipping for again physical damage.
I hope you dont put your laptop on your car driver seat and sit on it and go "durrrrrr it broken now and battery caught on fire." DONT SIT ON ELECTRONICS THINGS SHORT OUT. It's such a basic thing that dumb people dont seem to get. A cell phone has NO business in one's back pocket.
There's also unknowns as to using OEM chargers or not for some of those instances exploded charging at night.
Do some pop on their own? Sure. Lot of energy in those tiny things and nothing is 100%. But if you can point to all but 3 true examples out of how many hundreds of millions of iphones that's a PRETTY good track rate.
Note 7s were at risk of blowing up over 50% of the numbers that were shipped from what I understand, and replacements considered "safe" still blowing up. Pretty big smack in the face of the recall (government) now.
The reason why it's not major news is only a handful in the tens or hundreds of millions shipped in recent years isn't a noteworthy story; and of those handful some were user abuse to the phone or physical damage. It's well within a magin of error for manufacturing and such a mass scale/number. But many many more Note 7s in what, on sale for all but 2 months, have exploded than iphones in the past 2 or 3 years.
Finally, it doeant appear to be freak accidents in tiny numbers like iPhones but sheer negligence by Samsung (via Bloomberg) "original batteries that Samsung used for the phone were “slightly too large for the phone’s compartment.” The battery components were sometimes pinched, which could cause a short circuit, the safety commission said when announcing the recall on September 15th."
That's NEGLIGENCE by Samsung not caring what happened to people as long as they sold phones before the iphone 7 came out, not random freak accidents like the handful of iPhones.