Whenever you share information with somebody else, you are influencing them. Not in a negative way (hopefully), but in that they are learning and growing as a result.
Spending 1-on-1 time with someone is effective on a personal level, and sometimes this is the correct avenue. What you lack in quantity, you make up for in quality.
In other cases, however, quantity (read: amplitude) matters.
Imagine you've just purchased a new piece of IKEA furniture. It's flat-packed, and so it needs to be assembled. There are two options here: either someone provides you personalized instructions (either live or in an email straight to you), or an instruction booklet is provided.
(Aside: IKEA actually takes this one step further, since virtually all of their instructions are illustrations rather than written in a particular language)
Writing is a fantastic way to deliver your knowledge to the masses. The effort-to-value reward for a well-written bit of information is priceless. Invest the time once, and watch it pay dividends over time.