Yes its necessary! Oral is also necessary any time before, during, or after sex. I've always sucked cock before any penetration in my late teens. Mostly because men who approach me for sex do so with a purpose, so sucking his cock and working it based on how he touches me tells him that yes I am a good cocksucker. And also not every bottom, gay guy, etc gets quality tops right away (or ever). Some might not get any. So if a top that I like eyeballs me from across an adult theater or other cruise spot, or approaches me, I'm definitely going to get on my knees, unzip his pants and pull them down, and guide his already growing cock with the top of my tongue and slide it in my mouth. When I work it to where its half hard I start deepthroating a little. Then I do it more cause I love being deepthroated. If the top is the more aggressive type then I'll bury his cock in my throat till I almost choke........which will take a while cause I have no gag reflexes and I taught myself to breathe through my mouth.
All cocks release precum. At least the ones that I've sucked on. So when I taste it I mix it with my saliva so his cock can be lubed. I also 'pre-lube' his cock with saliva before he precums for just in case he can't wait to fuck me. But he usually puts me in whatever position he wants after he precums and fucks me. If he doesn't pull me up and I want him to fuck me, I'll ask him then bend over. I've never had a top refuse to fuck my ass. If I really like sucking his cock I'll just finish him off in my mouth. If I really like him, I'll lick the last drop of cum from his head, lick his shaft lightly with the tip of my tongue every few seconds while its throbbing from ejaculation..... Then i'll slowly suck his cock until its erected again and either ask if he wants my ass or finish him in my mouth again.
Yes I will go rogue and drain his load any way I want if he doesn't put me in position to penetrate me. I've never been with a 'dom' so I never depend on tops to show/tell me what to do. I know what to do and will let him control me if he wants. If not then I'll just keep sucking his cock because.......I really love sucking dick lol.
But that's what I always do and I've never had any complaints, nor has any cock ever gotten soft while blowing him, and he never takes his cock out of my mouth to jerk off for a little while to stay hard and puts it back in. If he does take it out he'll groan and hold it to the side cause he likes how I suck his cock and wants it to last longer.
So yeah oral is definitely necessary before sex so you can lube his cock with precum and saliva. Several tops eat my ass before fucking me but rarely will they put saliva in my hole. And hardly anyone takes lube in a packet. So yeah.