What is wrong with sending HTML and MIME message?

• Many E-mail and Usenet News reader programs, usually the mail and news reader programs that come with browser packages, allow users to include binary attachments (MIME or other encoding) or HTML (normally found on web pages) within their E-mail messages. This makes URLs into clickable links and it means that graphic images, formatting, and even color coded text can also be included in E-mail messages. While this makes your E-mail interesting and pretty to look at, it can cause problems for other people who receive your E-mail because they may use different E-mail programs, different computer systems, and different application programs whose files are often not fully compatible with each other. Any of these can cause trouble with in-line HTML (or encoded attachments). Most of the time all they see is the actual HTML code behind the message. And if someone replies to the HTML formatted message, the quoting can render the message even more unreadable. In some cases, the message is nothing but strange looking text. For this reason, many mailing lists especially those that provide a digest version, explicitly forbid the use of HTML formatted e-mail.
• HTML or MIME messages are larger and more wasteful than simple text messages. Using HTML or MIME in E-mail messages makes the messages larger in size by a mimimum of two thirds to more than twenty times. These will take longer to download and they take up more storage space than standard plain text E-mail messages.
  E-mail storage is important because many people retain copies of messages they receive and in the case of mailing list digests , the individual messages are combined in one large message and sent to the user at the end of the day. Some mailing list programs fail to format the digest correctly if HTML messages appear. In addition, many mailing lists archive the messages for periods of 6 months or more to enable users to search for particular past postings.
• HTML or MIME messages leave or include unwanted files (attachments) on the machines of the recipients of these messages.
• HTML quickly fills the memory of PDAs (Personal Digital Assistants like the Palm Pilot). In addition, many HTML messages are also completely unreadable on most PDAs.
• e-mail recipients may have set their background to something other than white, may have chosen a typeface which they find most readable and adjusted its size in accordance with their visual acuity, normal viewing distance, monitor size and screen resolution. All this fine tuning is completely erased by HTML e-mail