The way I see it, contraceptive is for the person using it.
So if the guy doesn't want the girl to get pregnant, or wants to avoid STIs - he should use the appropriate protection.
If the girl doesn't want to get pregnant, or wants to avoid STIs - she should use the appropriate protection.
(Both people want to avoid pregnancy/disease? Then both should use protection!)
That way you don't need to worry about what the other person is doing - you manage your own expectations.
If you're in a stable long-term relationship and have talked about it, then sure, you can rely on one person, but otherwise each person should, imho, manage their own contraceptives.
So if the guy doesn't want the girl to get pregnant, or wants to avoid STIs - he should use the appropriate protection.
If the girl doesn't want to get pregnant, or wants to avoid STIs - she should use the appropriate protection.
(Both people want to avoid pregnancy/disease? Then both should use protection!)
That way you don't need to worry about what the other person is doing - you manage your own expectations.
If you're in a stable long-term relationship and have talked about it, then sure, you can rely on one person, but otherwise each person should, imho, manage their own contraceptives.