movies can buffer and use much higher compression that can support chunks being lost or arriving late to save space, but that takes longer to decompress

game stream need low latency to be playable, which requires much less compression

a displays connection using dp @ 1080p60 = 3.2gb/s
thats zero latency and uncompressed

because of that streaming needs to use some compression, which takes time to encode+transmit+decode

Streaming services can use tons of data depending on settings.

Geforce Now free version can use little data due to it being configurable but then some games look terrible.