Viability takes quite a bit longer than the “first couple weeks” of a pregnancy. Before Roe was overturned in the US, viability was where the law drew the line nationwide.

People below 18 are still entitled to citizenship, still get counted in the census, are still eligible for child tax breaks. Pretty disingenuous to compare those to guns and voting and alcohol, which are widely regarded as adult things which require some degree of maturity to handle responsibly.