I think the question was why use ABC Info rather than the radar controller a flight is speaking to. It's a simple case of the Radar guys being too involved with traffic to get Wx, although he will if there is no other option. The Info freqs are there for that exactly -Information. I often use the service from GVA INFO when flying into Milan as those darn hills get in the way of the MXP ATIS.
As to why FR use the service more it may be a company cultural thing - they may have realised it's available and quicker and easier than listening out for entire VOLMETs or scratchy ATIS.