I'm not sure that would be the main reason. If you're concerned about security, pills/vasalgel/anything except condoms won't really save you from the worst consequences. Only a barrier method can be completely effective (and even that fails).
I would not call it completely effective. Someone who uses a condom perfectly, each time, every time, still has a 50% lifetime (35 year) chance of having a child.
And with more typical use a person is all but guaranteed to have at least one child during their life.
Condoms help reduce fertility (i.e. smaller family size), they do not eliminate the possibility of children.
Someone who absolutely does not want children does not really have any good solutions except avoidance. The typical advice is two methods of birth control at once (i.e. hormone plus barrier), but that's only an option for females.
That statement makes no sense. If the condom is not broken or slips off, there's no chance that a woman is inseminated. Unless the man has magic sperms that can teletransport themselves into a woman's womb.
0.98 ^ 35 = 0.49, i.e. 51% chance of failure.
Failure here means child conceived. And keep in mind that there is only approximately a 2% chance of having a child from each encounter, so condoms fail a LOT. (20% chance of a child if done at the right time divided by 3 days out of 30 where it's possible.)
Note that the low 2% conception chance is mitigated by looking at a failure rate over a full year, i.e. multiply 2% by the number of encounters in a year.
Perfect use of male condom: 18% chance of conception after 10 years. Typical usage: 86% chance of conception after 10 years.
Even "the pill": 3% chance at conception after 10 years with perfect use. 61% chance of conception with typical usage.
Everyone thinks they use contraception correctly. It may be true for anyone reading this forum, but if you're looking at policy, you have to account for typical usage. Education campaigns can move "typical" closer to "perfect" usage, but IUDs and sterilization are pretty much the only types of birth control that offer more than 50% chance of not conceiving in 10 years.
I would of course absolutely advocate using a condom with any new non-fluid-bonded partner.
Having said that, there definitely are non-technical issues that can make pregnancy more final than an STD (moral opposition to abortion, not wanting the child while the woman does, ...)