Though when "lore-wise" is being used as a reason for the gender-locks it is a weak argument, because it's a fictionally imagined universe, which is also most likely imagined and designed while prioritizing the gameplay first and story second, with many of the decisions chosen to most likely serve the gameplay purposes since it's a game first, and it's even a high fantasy fiction where imaginations can go towards every course.

Since it's a franchise that started with and for the game, there is also no laid out background before BDO's release of its universe where they needed to stick to and rely on for the story which cannot be altered and changed.
There is no valid reasoning for why they cannot imagine males in the BDO universe who would be able-bodied and would choose to become a Dark Knight or a Guardian and to just say that the story was designed so.

So far, I've had several friends who refuse to even try the game simply because of the gender-lock and it has annoyed me to be honest, if there were more alternatives for most classes or some classes were not gender-locked, I'd accept and understand it and could even use it as an argument but unfortunately it's not so.

We don't need more classes anymore, we have enough. It's time where PA should focus on contents and making the game better and fixing lots of desyncs and bugs, improving the classes we have.

This.

Or I mean, for the sake of everyone's happiness do release a new male class but then stop it. The dev focus on dishing out "new" classes regularly is ruining the game. This is not League of Legends. 

wtf... just add more female classes, make 4 twins females next time! the more females the better.

Skipping aside that I thoroughly dismantled your "why are there no male DK or male Zerker" question, there is a valid reasoning -- Developer intention.  Like it or dislike it, facts don't care about your feelings.  The devs decided to create class specific lore that correlates to the class' specific sex. 

They've said -- on numerous occasions -- that class sex-change will not be a thing in BDO.

Let's be clear here -- there's no "valid reason for you", as "there is no valid reason" is merely your own opinion on the matter.  Because, aside from lore -- like I said, and you didn't point out, there are tons of other reasons in this thread why removing gender-lock wouldn't be feasible.  My biggest reason is its tangibe effect in PvP.

The fact is, this is how the developers deliberately designed their game.  Don't like it?  Design your own MMO or play the plethora of other games that don't have gender-locking.  That's what it comes down to at the end of the day.  They will not change this, ever.  They have created, and will continue to create, "class counterparts" -- IE: Archer is male "Ranger", Guardian is female "Berserker", Valkyrie is female "Warrior", Sage is male "Sorceress".  That's what we have to work with, and if this (IMO) minscule aspect affects you and your friends so much, then find a different MMO with action combat as good as BDO.  Good luck.  Class sex-changes will not be a thing in BDO.

Is that why there are 17 female classes with 9 male counterparts? Yes, makes sense, the math displays it quite clearly.

And I'd advise you to stop trying to drive away other players from the game as well as potentional players just because they disagree with you or have their own preferences and suggestions as it neither serves the game nor its company at the end of the day. As far as I know, the game wasn't made solely for you. Good luck to you as well.

Hello, female here.

Keep bring more female classes, thank you

Hello, male here.

Bring more male classes, thank you

Preach it brother.

Suggestion for new male class: Base it on the Fadus Warrior Chief. 3 weapon modes: dual swords, big ass halberd, staff (caster). Similar in the vein of Archer/Shai that you don't have to choose between them. Would be interesting imo.