Southwest Airlines flights were delayed and cancelled this week due to an outage in their third-party weather provider. I understand if they have a streamlined business process for getting weather data to their pilots, but is that really the only way for them to get their en route/destination weather? Is there a reason they can't obtain and use the same type of briefing a GA pilot would use?
Airlines operate under the requirements of their Operations Specifications, or OpSpecs. One of these will state what the approved sources of weather information are. For a large airline, that weather provider will be providing weather to the pilots and to the dispatchers, ensuring that everybody has accurate & current info. Most of the time, what you can get from any number of internet weather sites will basically match what you get from your airline, but the requirement is there so that the crews are always getting the same good info as the dispatchers.
And when you aren't getting that info from the approved source, per the OpSpec, you can't operate (unless there is a backup source that's approved).
On a clear day, it probably wouldn't much matter where you got the info -- "no alternate required, destination is landing to the west, 30 knot headwind in cruise, okay let's go." But the system and the requirements are set up to keep things safe even when conditions aren't all benign. And the uniform requirement is, get your weather from an approved source, and only then, you can launch.
Airlines usually use a third party (although Northwest infamously used their internal weather department) to get their weather because there's so much data to be obtained.
In the Center, we aggregate weather data from the NWS and NOAA that includes METARs, TAFs, SIGMETs, etc., as well as upper air data (GRIB format), GOES, and NEXRAD. Airlines do the same.
They typically fly longer routes than GA aircraft, at higher altitudes, and have larger fuel concerns.
It makes sense for them to suspend operations if they can't get that data.