I think it also goes back to what "one" person deems a word to mean may not necessarily be what another person sees that word to mean. Which takes me back to the idea where emphasizing written word over spiritual truth will always bring different results.
In the King James, surprisingly, it's only used eleven times. See if there's any pattern that emerges as you go down the list of passages.
Rom 7:14 For we know that the law is spiritual: but I am carnal, sold under sin.
Rom 8:7 Because the carnal mind [is] enmity against God: for it is not subject to the law of God, neither indeed can be.
Rom 15:27 It hath pleased them verily; and their debtors they are. For if the Gentiles have been made partakers of their spiritual things, their duty is also to minister unto them in carnal things.
1Cr 3:1 And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, [even] as unto babes in Christ.
1Cr 3:3 For ye are yet carnal: for whereas [there is] among you envying, and strife, and divisions, are ye not carnal, and walk as men?
1Cr 3:4 For while one saith, I am of Paul; and another, I [am] of Apollos; are ye not carnal?
1Cr 9:11 If we have sown unto you spiritual things, [is it] a great thing if we shall reap your carnal things?
2Cr 10:4 (For the weapons of our warfare [are] not carnal, but mighty through God to the pulling down of strong holds;)
Hbr 7:16 Who is made, not after the law of a carnal commandment, but after the power of an endless life.
Hbr 9:10 [Which stood] only in meats and drinks, and divers washings, and carnal ordinances, imposed [on them] until the time of reformation.
I'm not really seeing where "sexual" is coming into play in the context of where this word is being used. Perhaps the translators have again chosen a poor word in place of the original rendition?
Or maybe it's because Websters isn't taking context under consideration in it's rendering of the word?
Strongs puts it this way . . .
1) fleshly, carnal
a) having the nature of flesh, i.e. under the control of the animal appetites
1) governed by mere human nature not by the Spirit of God
2) having its seat in the animal nature or aroused by the animal nature
3) human: with the included idea of depravity
b) pertaining to the flesh
1) to the body: related to birth, linage, etc