I used to buy Blu-rays, but these days I buy and rent a lot of movies on iTunes, and occasionally Vudu, because it's just so much more convenient to be able to choose a movie and start watching without having to get up from the couch, find the disc, put it in the player, etc.
The three main reasons I used to buy Blu-rays were quality, extra features like director's commentaries, and the fact that I didn't like the idea of investing a bunch of money in buying movies on a single streaming service and not being able to watch them on another.
These days, the quality of 1080p and 4K content on iTunes and Vudu is really spectacular. Both services support Dolby Vision HDR and Dolby Atmos. They can't match Blu-ray in terms of sheer bitrate, but I honestly can't tell the difference, and I'm really picky.
iTunes and Vudu also both include extra features (when available) when you buy a movie.
And, amazingly, the Movies Anywhere service now makes it possible for you to buy a movie on one service, like iTunes, and have it immediately become available in your account on every other participating service you use (Vudu, Amazon, Google Play, etc.).
iTunes always has a pretty big rotating selection of less recent movies on sale for $8 or sometimes even as little as $4. I've bought so many great movies that way!
Another iTunes secret: if you buy a movie that's only available in 1080p, but it later becomes available in 4K, the version in your library will automatically be upgraded to the higher quality version free of charge. The only exception is if the new version is treated as a separate release (like a "remastered", "special edition", or "director's cut" release).
Also, if you buy a movie on iTunes without any extra features but they later add extra features, you get those for free too!
So yeah, it's pretty hard for Blu-ray to compete these days.