Every type of retirement account has different contribution limits. The accounts with the most generous contribution limits favor those fortunate enough to have employer support and high incomes.
The nation would be better served by unifying contribution limits and other account requirements for every type of retirement account. Doing so would be especially helpful to employees of small businesses, who often are limited in how much they can save for retirement by the low $5500 contribution limit for IRAs (as of 2014).
A simpler, more fair plan would be to have a single contribution limit of $17500 (the current level for 401(k) plans) per person. Employer contributions would count towards that limit as well (as opposed to 401(k) plans which allow for up to $52000 total).