Sword out - enemy threatened - bow out - enemy not threatened - does this make sense?

[Vicid]

So if I am holding my melee weapon while standing next to an enemy it is 'threatened' I believe this means that my allies attacking it will get some kind of bonus (for example a rogue can do the sneak attack because the enemy is paying attention to me - so he can stab in the back)

What is strange to me about this, is if I end my turn with a ranged weapon this goes away. That might be interesting as some kind of tactical choice, but I can switch weapons at will after taking all of my actions. This means it is best to end a turn with a melee weapon out no matter what actions I took on a turn.

A) It's annoying to have to micromanage this aspect of the game. If I can switch from ranged to melee at will, why doesn't the game just consider my melee as always out when I end my turn? If it comes into play (like an attack of opportunity is triggered) just switch and do it.

B) does my AC change if I'm switching from a sword and shield to a bow? Yes I know that makese sense, but again I'm able to switch at will before ending my turn so why even bother?

[Vicid]

Just tested. Equipping a shield but having my ranged weapon out does not lower my AC (I still get the bonus from teh shield) but I confirmed my character did not take an attack of opportunity when an enemy ran away from me.

I guess I'm just mad it's silly I need to change to melee at the end of my turn, especially as this is an action that does not consume any sort of action (To be clear I don't want it to, but if it's free the game may as well do it for me)

[Nauct]

There are situations you'd want your ranged weapons out. Like Commander's strike from Battlemaster. Maybe you have light on a weapon and don't want that effect etc.
I'm in the habit of always changing to melee weapons at the end of my turn. I hate when things are automatic, like automatically attacking with your offhand and the default is set to on for some ungodly reason

[Chaosolous]

You have disadvantage on ranged attacks while close to an enemy when using a ranged weapon. The logic is kind of fluffy~wuffy but it does follow some semblance of sequitur.

[TaKo]

the game doesnt manually end your turns for you, switch weapons before doing so(F hotkey)

you cannot threaten with a ranged weapon(and therefore no attacks of opportunity with ranged weapons), in fact ranged weapons get disadvantage when in melee range of others armed with melee weapons

[Cartesian Duelist]

https://www.d20srd.org/srd/combat/attacksOfOpportunity.htm