Building a music library makes sense if,
1) you own a large enough collection of rare CD’s that are sourced from analog masters and currently not available on Qobuz/Tidal. I own over 500 such albums, majority of them still not available on any streaming services and sounds much superior than streaming counterparts.
2) you plan to buy DSD downloads….do this if your system is high resolution and you can honestly tell apart DSD from Qobuz stream, otherwise Qobuz files in 24bit/192kHz is pretty darn good for most part.