Why would a Roth 401k be odd? Aside from a matching contribution, some of us are disqualified from contributing to a a Roth IRA and have preconditions that prevent us from doing a backdoor Roth IRA. Also With a Roth 401k, one can contribute up to 18k/year if one choices not to contribute to a traditional 401k. I think that’s a lot more than most people can can contribute to a Roth IRA.