I am curious why exactly the free float rail/handguard has become pretty much the default for all newly produced ARs.

Most all new ARs take more money and effort to set up for shooting now because you need to buy sights and generally rail covers unless you always shoot with gloves.

Since most guys aren't shooting with NV the rails usually just hold a front sight, though some guys just go straight to an optic with no iron sights at all, and the vast majority doesn't even mount a white light on the rail. Even glancing through the picture thread here you see tons of railed carbines with only a flip up front sight or no sight at all.

So, from a pragmatic perspective, what is the reason that most ARs are being built this way anymore?

Is it less costly to manufacture and assemble low profile gas blocks and rails over FSBs and plastic handguards?

Is it a false assumption that most buyers are attaching lots of devices to the rails?

Is the rail setup more durable than the old FSB setup?

Is it simply marketing or targeting what the consumer wants because those guns look cooler?