I haven't looked this up but I'm pretty sure, historically, bayonets did become superior to spears. Notice how spears are only available to militia troops like partizani (and those blue dudes from Prussia, oh and sailors). These men receive very little training in melee. However, the line infantry have basically been training for years with their rifle and bayonet.
When I get spawned with a spear, I use its length to my advantage. I usually stand back from a big fight and take jabs at overwhelmed opponents (pikes are best for this).