What kind of services do mutual funds offer that their equivalent ETFs don't?

When you invest in a traditional (not exchange traded) mutual fund, you generally have an account with the mutual fund company directly. Your money goes straight to them, they send you statements, you log in directly to their website, etc. If you interact with a broker at all (not required), the broker is simply acting as a sales person for the mutual fund company, perhaps getting a sales commission from the mutual fund company.

With an ETF, you do not interact directly with the fund company at all. You are required to purchase shares through a broker, and your account, statements, and website access are all managed by the broker. The fund does not pay any sales commission to the broker; they get paid through any transaction fees they might charge the investor. (These days, there are often no transaction fees.)

Related: What are the important differences between mutual funds and Exchange Traded Funds (ETFs)?

ETFs and mutual funds have many similarities and various differences. There are different types of ETFs and different types of ETFs so the following is a general comparison of ETFs and open ended funds:

MUTUAL FUNDS

• Actively managed
• May have minimum holding periods and penalties for selling sooner
• Usually bought or sold at the end of the day
• Trading occurs between the investor and the fund
• Actively managed
• Higher fees and higher expense ratios
• Higher minimum investment
• No limit on the number of shares that can be issued
• Share price (NAV) is based on value of assets held and calculated EOD
• Cannot be sold short
• Tax disadvantaged if shares must be sold to raise cash for redemptions

ETFs

• No minimum holding period
• Are more cost effective
• Trade like stocks throughout the day (share price can differ from the NAV)
• More likely to be passively managed (index ETFs) and therefore, lower expenses
• No minimum investment required (some brokers offer fractional shares purchases)
• Can be sold short
• Passive management provides tax advantages "in-kind redemptions" does not incur taxable realized gains (creation and redemption)

A major difference between a Mutual Fund and a corresponding ETF is the consequences of daily trading:

• if you buy a mutual fund, the respective company, in your example Vanguard, needs to act accordingly and invest your money in the underlying stocks / securities. If you sell the Mutual Funds the next day, they again have to act and sell the underlying, to produce the necessary cash for you (of course, they would only do that with the accumulated changes from all buyers and sellers every day, but it is still a daily effort, and produces trading cost).
• if you buy (or sell) an ETF, you find a partner for this trade on the exchange. Vanguard has nothing to do with the transaction, and doesn't need to act in any way. Only if the market demand started to deviate strongly from the supply over longer periods, they would have to 'create' (or 'dissolve') a large block of the ETFs, to balance the market.

This is the main reason ETFs have a cheaper cost than the otherwise identical Mutual Fund.

In addition, they often offer DRIP investment, which buys you fractional shares for your dividends, but that's probably a minor cost factor.