You are comparing apples and oranges because you are missing WHY the law recognizes responsibility in a progressive manner. There are two issues here:
- the ability to make cognitively INFORMED decisions
- the rights of the individual
So if we look at the items you mention
Join the military - 4 years.
This requires the ability to understand the legal implications and to be able to continue to make a series of cognitively Informed decisions AFTER you make the initial decision.
Furthermore you don't have any fact based advisors to help you make these decisions. So not only are you on the line ethically, you are also on the line factually.
While I would argue that even 18yo aren't really capable of this, the societal consensus is that 18yo have sufficient congitive processing to do this in the framework of a hierarchical military. Are there 15yo who could do this? sure but not many, so you have to draw the line somewhere
As for rights - there is no imposition on the rights of the person doing the signing up to be precluded from this decision until 18
Get a credit card - 7 years.
Again here the issue of Cognitively Informed consent comes into play. The issue is whether you can cognitively draw enough FACTUALLY INFORMED decisions for them to be legally consistent and bindig
as for rights - there is no imposition on the basic rights of the individual if a corporation won't contract with them
Rent an apartment - 1 year
This is simply a shorter term case of the Credit Card for which your 7 year impact is the time period it takes for something to disappear from your credit record - in which case the duration here is also 7 years.
Note also that in the latter 2 cases, if a minor has a legal advisor - such as McCauley Culken did, you can get emancipated at a much earlier age by demonstrating certain cognitive competencies.
Now in the case of abortion the FACTUAL basis for that decision support is provided by the MDs. So only the ethical component of the decision is the one that the minor needs to make
Furthermore, unlike the prior examples, removing this right from the minor requires an intrusion into their physical bodies in a manner that our Constitution only allows in the most compelling circumstances.
So in balancing the common law rights of parents against the explicitly enumerated protections and rights of the individual, the balance goes to the minor unless the legal guardians (parents, state, ad leitum) can demonstrate that the individual is cognitively unable to make such a judgement.
Basically parents don't have the right to force their children to have the parents beliefs. Yet you want The Government to violate those most fundamental protections siimply because YOU don't like the outcome.