Why is apples iphone display not 1080P yet?

The good android phones that cost more then the mid range phones have 1440p 1080p displays yet apples is slowing catching up to that when android been doing it for awhile? Iphone 6s plus is the is one of the iphones to have a 1080p display but that phone came out in 2016 why i say slowing catching up to full HD lol

They probably have the features for 4K on a phone, however companies release features slowly for extra money because that's what life is all about now (dollar billz yall)

Two reasons
1 The display is too small to notice 1080p resolution.

2 App development is done based on pixel ratios, not screen resolution. Easier, quicker and cheaper to develop apps.

Sort of don't get the premise. You said the iPhone doesn't have a 1080p display then list the 2nd iPhone to have one. (The iPhone 6 Plus was the 1st & the 7 Plus is the 3rd).

Full HD is 1080p by the way.