A large corporation opens a website to serve its customers in Eastern Europe. Here, the use of the FONT element means that the user must delete the specified fonts from his system in order to read the text in his native language and alphabet. The viewer, using Netscape 3.0 on a Unix workstation, sees some approximation of the author's font, but here the letters appear so crowded, the kerning and leading so deranged, that the author's exquisite taste has become an ugly hash. The font tag is a hindrance to communication over the World Wide Web because it makes too many assumptions about the user's system, browser, and configuration. Cascading Style Sheets, on the other hand, negotiate between author and viewer to create a carefully-designed appearance that is accessible to all.
People create web documents for many reasons.
If you have something to say, information to provide, a message to preach, feelings to express, a product to sell, then it's in your interest to make your work accessible. Smart web authors, who want to get their message across, stay far away from the FONT element. The FONT element is broken in current implementations, is prone to cause unpredictable and unavoidable data loss, and is quickly becoming obsolete with the advent of Style Sheets.