The real question is:
Why Sony has to respond to Gamepass??
Because it's gaining traction. Consumer that try it, for most of the cases anyway, really enjoy its value for money and the access to games that they were likely to pass. Developers are starting to see value on it as their games reach a broader audience and helping build brand recognition, and in the world of Games as a Service it also brings players to play online and spend on microtransactions.
Games As a Service are not a fad. We can track it from the early MMOs to Fortnite to Gamepass. If Sony don't react accordingly they might be in an catch up situation sooner than they think.