Are higher end preamps worth the investment when you are only streaming Tidal & Spotify ?

Assuming based on your equipment you are looking for an analog line-level preamp.  In my experience, having a good high -fidelity preamp is very important in any listening environment.  Digital reproduction in general has certainly come of age as has streaming digital.  If you have really good resolving digital source devices, be they a good CD transport or music server or streamer, and a good resolving DAC, you can absolutely tell the difference between those sources as well as the equipment that processes them to your preamp.  Having every piece of equipment in the audio chain from the source to the speakers at the highest fidelity level you can afford will allow you to have a satisfying listening experience. In the digital world, I have found that minimizing noise and especially jitter has profound effects on the quality of the musical reproduction.  A high-fidelity preamp will allow you to hear the subtle differences between changes in your digital sources.