Mercedes is well-known in Europe for their truck division. The cars are a sideline!
And aside from the higher-end series, the sedans come equipped with cloth seats and are absent of jewel-encrusted appointments and exotic woods. So their are considered well-built mainstream vehicles elsewhere in the world.
When MBs were introduced to the US, there were marketed as luxury vehicles and were lavishly equipped (as were the stickers).
So they are branded as luxury vehicles today, and have an enviable history of quality and safety...although they may lose their reputation for "quality" if they don't fix things soon...
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What I like best about MB is their typical 9-year model style runs. So you can procure an 8-year old vehicle for a fraction of the new car cost and still be driving a fresh design. I believe DC is shortening this to about 6 years though...