Much like how many of us simply English online, many of them often don't bother switching between hiragana and katakana since most native Japanese speakers don't get confused just because of the switch. At first, that's just due to laziness and convenience, but since it pretty much became acceptable and understood, it also became just a different way of writing the same word, so people do it intentionally.
The same applies the other way around, too; I often see letters that should be in hiragana in katakana instead.
