Does it matter?
They are choosing to fill their time with you. For a reason - i. E. they like you!
OP, are you worried they don't really like you? Or that you aren't as close as you'd like?
A lot of friendships start off fairly transactional, think of new mum friends; you've just had babies, are at the same baby class, get talking, meet up in mat leave, have a good time. Then everyone goes back to work and has less time. Naturally some of those friendships fizzle out over time. But the ones you've truly clicked with, they are your 'tribe' . Will they be perfect friends who always show up and put you first and never do something to upset you? No, because that's not realistic. They have their own lives, troubles and tribulations (which you can help with if you can).
There will always be some friends that are transitory imo and I'm not offended anymore if we are not friends forever or best friends.
Try for one or two very close friends and enjoy the rest for what they are.
Sometimes it's hard when there is a mismatch of feelings re the intensity of the friendship. However you cannot change people, all you can do is continue to seek your 'tribe' - those people that love you for exactly who you are and you them. Where the friendship is easy.
Also friendships take time.