Jeez maybe it's just me, not a very smart user, but after at least 6 years with iPhone5, just before changing it, I discovered how to raise the volume without logging in the phone first:

I press the home button, Siri show up, and THEN the fucking raise/lower audio buttons are working.

6 years typing the fucking pin just to raise the volume.
6 fucking years missing notifications and calls just because I forgot the fucking volume on the lower tone. Almost lost a girlfriend for that.

Sounds like a bug though.

You can change the (media) volume via the control center or using those buttons on the left side of the phone. I'm not sure that's what you asked for though.

@IAmAnIssue yes, I would like to change volume with the volume buttons on the left side.
Without touching swiping or logging in.

It seems something basic to me, but I wasn't able.

I had to:
or log in with pin before using buttons
or press home, swipe up, swipe left, swipe the volume. FOUR fucking actions. (or more if I miss a fucking swipe)

I just wanted to use the fucking left buttons.
For example when I'm in the kitchen cooking and my hands are wet.

It's a fucking mechanical volume button.

Now at least I just press home (long) for Siri and button

It just works™