Thunderbolt 3 (and probably USB4) requires chipped ('active') cables at lengths over 0.5m, but considering you're pumping 40Gbit of data over it, it kind of makes sense.
For Lightning, yeah, there's basically no reason except for the 'Made For iPhone' program, and it isn't even effective at that since Chinese cable makers just clone the keys of the official stuff.
It could, but it already was hard for Intel to get Thunderbolt adopted because the controller is rather expensive. My guess is that they assumed most people would only use it for short distance connection and thus they moved the cost of EQ to chipped cables for those who would truly need it.
Not exactly - at very short ranges, you can use DAC cabling, "Direct Attachment Cable". Those directly connect SFP signals, but afaik they still have circuitry inside its just easier because the cable is known length and characteristics - in exchange the cable is rather thick and unwieldy. Generally it works well inside rack for connecting servers to ToR switches and that's it.
40Gbit DAC is even more annoying because unless the cable is a bit more active, it's essentially 4 10gbit DAC in one sheath.
there is no such thing as 40G ethernet. you can see this easier with optical - there are literally 4 cables inside the one thick cable. you're talking about quad ports - 4x 10G connections in one wide QSFP. in fact, all a breakout cable does is take the 4 wires in that 40G cable, and unwraps them. Ethernet currently goes to SFP28, which is a 25G connection. fibre channel (as in SAN, not LAN) in theory currently goes to 128G, and in practice you can buy buy hardware that goes to 64G. FC cannot run over copper.
Second, yes, some does require active cables with DAC. which does not stand for "cable" like the other comment says. DAC is direct attach copper (as opposed to optical). Without an active cable you're limited to 5 meters, although you can risk it and get a 7 meter passive cable. usually, 7m is already active, and 10m+ is guaranteed to be active. The reason you can even do 10G over copper is because it's cat6. Have you seen that cable? It's twinax - more like the cable from your TV antenna. That's not viable for a phone.
What you are talking about is 10G base-T. That does not need active cabling. but again, you can't compare that to a tiny thin lightning cable.
For Lightning, yeah, there's basically no reason except for the 'Made For iPhone' program, and it isn't even effective at that since Chinese cable makers just clone the keys of the official stuff.