The volatility that shook the markets in late January and early February 2018 was a reminder to all investors about what they control and what they don't. Out of their control: the direction of interest rates, inflation, and the trajectories of the stock and bond markets. Within their control: savings rates, asset allocations, expenses, and tax treatment of their investments.
Making an IRA contribution helps bring together several of these "take control" elements into a single action. Boosting savings is one of the best ways to gain control in uncertain market environments; doing so in a tax-sheltered wrapper like an IRA, and selecting a low-cost investment to put inside of it, helps give the account's return potential a further boost. Investors can also use their new IRA contributions to help bring their portfolios' asset allocations in line with their targets: Nine years into the current bull market, many investors are light on bonds, so new IRA contributions might reasonably be directed into the asset class. (Punching your holdings into Morningstar's X-Ray tool is the best way to see how you stand.)