Maybe the reason for this change is that people simply use faster computers, and have faster internet connections, than they did the last time the question was asked.
On a practical note, one of the disadvantages of plain text is that foreign language characters aren't supported - for example, if I was to set a story in Britain I might want to use the UK pound (money) sign, and it isn't part of the ASCII character set but is supported by HTML. Foreign names and words also often omit umlauts and other special accents that are possible in HTML
Re the appearance of so many unexpected line breaks in stories - I think that sending them by email causes the problem. Most text email programs insert hard line breaks if a line is over a certain length, even if it is pasted in without the breaks.
