on the early game,
zerg can easily mass roaches+zergling or do the banel bust(if got weak wall).

while terran and protoss they have to spend money on building a few racks, factory or a few gateways.

And zerg can easily defend terran's early reaper* harass / scout with queen+sunken

early helions can easily use speedlings on creep.
And early zealot rush? It's nothing. Mass speedlings can easily pawn stalkers.

Let's not take it as individual race.

Let's take it as ZvP and ZvT early game.
*changed marauder to reaper

reapers are only useful if you plan to sneak and utilize the cliff to gain advantage and use hit n run tactic.

10 reapers vs 20 speedlings in an open space is sure bye bye to the reapers because of their low hp.

you're contradicting yourself here.
reapers = imba early game
zerg = strong early game

what?

my point is reapers are conditional and need good skill player. if it is that good, all Terran players sure produce reapers most the game already.

as a Zerg player, I'm not scare of other races during early game, except another Zerg player.

Want to swarm me with tier 1 units? Let's see my zerglings better or your marines/zealots better.

Want to go for reapers? then your base is quite open and I might tech to hydra waiting for you, or I even do a 10 pool rush. My opponent need to gather quite some gas b4 reapers can come out ... unless he's a very good defense player, else my speedlings already swarm to his base and surround his barrack.