I can see several reasons to collect CDs.
One reason is that several of the big companies only invest in commercially viable artists. Some smaller independent record companies on the other hand, for example when it comes to jazz, don't put their music out on streaming platforms at all (because they don't get paid).
I also buy records to support the artist.
Another reason could be that older versions of music released on CD are better mastered than the remasters available on the streaming platforms. It's actually quite common. This happend for example with all the older Tom Waits recordings. Another example are the records once recorded by DECCA with Rolling Stones on CD from London Recordings. They are much better sounding than todays crappy remasters.
The third reason is that music you are listening to can suddenly disappear from the selection on your streaming plattform - or not exist at all.
A fourth, as others have already mentioned, is that you play entire albums in a more focused way. I would not be completely surprised if the price of used CDs will soon increase. At least for some CDs. I think I already see tendencies towards that.