I was going to answer "patents" because that's what I had read in the past (that LZ '78 was encumbered by patents while LZ '77 was not), but this wikipedia talk

I was going to answer "patents" because that's what I had read in the past (that LZ '78 was encumbered by patents while LZ '77 was not), but this wikipedia talk page: https://en.wikipedia.org/wiki/Talk:LZ77_and_LZ78#preference_of_LZ77_versus_LZ78_algorithms https://en.wikipedia.org/wiki/Talk:LZ77_and_LZ78#preference_... suggests that it's not just patent encumbrances.