Well, considering this "let's bring back dead sitcoms" is relatively new...(but we've had, what, four of them in last few years?)
Not just us, but the UK is doing it as well (Cold Feet returned and Porridge got a reboot). Though they've been doing it on a smaller scale in the way of 1-2 episode specials with other shows for many years. I remember Vicar of Dibley airing these specials years after the series officially ended. Absolutely Fabulous ended in 1995, then specials in 1996, full season in 2001, specials in 2002, full season again in 2003, then specials in 2004, 2011 and 2012.
But we've seen reboots/revivals before in various forms over the years...The Twilight Zone, The Outer Limits, Alfred Hitchcock Presents, The Brady Bunch (tried it twice and failed both times), Fantasy Island, Burke's Law, Beverly Hills 90210, Melrose Place, Dallas, Get Smart, Leave It to Beaver, Gidget, Mission: Impossible, The Munsters, What's Happening, WKRP in Cincinnati, and Sanford and Son were a few.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian