While I understand the reasoning, having citizens either younger than 18 or otherwise vote themselves without their parebts voting for them would increase the voter base yes but that would help counter other issues. For example in states like Florida, Alabama, Texas etc. they spent decades making sure voters were disenfranchised and removed from voter rolls meaning fewer registered voters in that state, so either those states make it easier to register and to vote increasing the voter turnout and potentially the vote for policies they would want, or they decrease the voter turnout and have less of a say in who becomes president. I.e. if you were a Republican in Iowa or something and wanted to pass a national abortion ban but it was a presidential election year and it was close to the line without the electoral college you could increase the vote, potentially, for the Republican candidate, by passing a law saying highschool juniors and seniors (16-17) can vote in presidential elections, this would increase the popular vote margins for Iowa, not knowing how they would vote overall for certain, assuming the highschool students now able to vote vote the same as the average of the state that means it would be an average distribution, but let's say that Iowa is pro republican (not this current election cycle but another) but also pro choice especially among the youth would be most affected by it increasing the vote share of the state to those who would be disproportionately troubled by that policy could backfire, the same works the other way with guns and lets go with Texas, if Dems keep Texas but then try passing very unpopular gun legislation in Texas that could make Texas red again for a presidential bid. Having more voices decide who runs the government, how they run it, and what policiers to go after thé better.

it isn't perfect but it corrects itself somewhat.