Stoutstien
lunk
It's not just the extra attacks. it's the extra attacks combined with the fact that it will takes more attacks to overcome the threshold in which combat would end.I disagree that multiple attacks slow the game down much.
In my experience it's spells and figuring out how they work that is the most time consuming. Second to that is figuring out status effects and class abilities.
Straight up attacks? Usually just a 15 second roll, check and damage roll.
You're not just adding actions you're adding total rounds which means more spells, status effects, and other potential delving into pages to resolve actions.
If you want to avoid the whift effect, adding damage on misses or just giving them an auto hit at certain intervals is easier, faster, and more engaging than adding more attacks. Not to mention that attack volume is one of the leading things that cause system wobble because without fail there's always going to be some combination that allows you to stack more attacks for more damage cheaper than anticipatedly budgeted.