A lot of protestants do not believe baptism is necessary for salvation. It all depends on a careful interpretation of John 3:5
"Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God."
Now, "born of water" could be (and probably is) a euphemism for physical birth. The reasoning is thus: Christ is talking about being born twice. Nicodemus says "How can you be born twice?" If being born of water meant baptism, and there was another birth of the Spirit, then you'd actually be born -three- times.
Clearly, from John 3:3, we are talking about two births, not three. Therefore, "born of water" is a euphemism for physical birth and born of spirit is being born-again in Jesus Christ. This is what many evangelicals believe.
HOWEVER- I also believe people should get baptized, and there may be spiritual power in it because Christ underwent it, and it's been a tradition for so long and it would be really dumb to go to hell over the technicality (although I do not understand my God to be one to judge on something like that). All the same, why risk it? Jesus did it, let's do it too, if nothing less than to honor the way he showed us.
But necessary for salvation… strictly speaking, probably not, but play it safe anyway, cause' its eternal life we're talking about here.
Play it safe argument applies to infant baptism too. It doesn't hurt anyone if it's ineffective, at worst it's a public ceremony to dedicate a baby to Christ, at best it actually has a saving effect. Either way, why not do it and hope it has spiritual impact?