A good reason to use Vanguard as a company is their mutual funds. (Though you can trade Vanguard mutual funds elsewhere, they'll usually come with transaction fees.) Mutual funds are arguably superior to ETFs for many investors, in a few ways.

* Mutual funds are fractional by nature — you can trade as little as $1. Right now, only a very small handful of brokers support fractional shares of ETFs.

* Since MFs aren't traded as whole units, you can set up automatic investing. Let a certain % of your paycheck go into the MF every month. Not possible with ETFs on most platforms, a notable exception being M1.

* Since MFs only settle their NAV once a day, you're discouraged from compulsively checking your portfolio every few hours. If the market is temporarily down, you won't see it reflected in real time. Some people consider the real-time aspect of ETFs superior, but for long-term investing, this lack of an instant dopamine rush means it's easier to just not think about it. Fewer emotional decisions.

* Mutual funds can be "funds of funds". Regulations prevent ETFs from doing the same thing. A good example of a FoF is Vanguard's target date retirement funds, which are nearly exactly equivalent to a Boglehead-style three-fund portfolio.

MFs have a reputation for being expensive, but Vanguard's have some of the lowest fees on the market. MFs also can be tax-inefficient, but Vanguard has patented a loophole that makes them as efficient as ETFs when held in a taxable account.

Vanguard is also a great company; easily my favourite investment company. Its ownership structure is inverted: The company is collectively owned by its funds, which means that you, as a MF shareholder, will own a part of Vanguard.

Note: The above points about MFs are largely moot with robo advisors like Betterment.