One of the important aspects of these events as milestones in representation is that television has (or at least had) a very different reach than most other forms of media. Gay/lesbian kisses in movies aren't necessarily expected to be mainstream, even a big blockbuster isn't going to attract everyone to come see it in the theaters, while network television is broadcast and assumed to be available for most people's homes barring remoteness or urban reception issues where most people probably had some basic cable. Historically, that made anything that happened on a major network (or even widely syndicated) a much bigger deal.