Why is it that the B17 flying fortress is so much more known/used than the later developed B29 during the period of WWII?
Whenever I hear speaking about the heavy planes of WWII it always seems like its focused on the B17 rather than the more modern versions of it at the time.
I suspect because you're reading more histories of the European theater than the Pacific one. Since, as u/Geotolkien noted, the B-17 was developed pre-war, it was able gain earlier combat service and had a head start on entering public consciousness. However, I think it’s worth nothing why the B-17 was able to begin earlier: The bomber mission in Europe didn’t require the range of a B-29. It’s roughly 600nm from England to Germany (basing off a London-Berlin route), which fits well within the B-17’s combat radius. So long as the allies were able to use Britain as a base of operations, the RAF/USAAF had the ability to strike most of the Reich/occupied Europe. While technological developments continued on the B-17 throughout the war (most notably the addition of the chin turret on the G-model), the basic airframe itself was solid for the mission at hand and did not require many changes.
In the Pacific theater, large-scale bombing of Japanese production and population centers couldn’t’ begin until there was an airfield within range of the Japanese Home Islands. This thread does an excellent job of explaining the overall Island Hopping strategy. Once those bases were established, the only plane that could make the 1,300 mile journey to Tokyo and back was the B-29. While outwardly similar to the B-17, the Superfortress was a whole new breed of airplane. With her pressurized cabin and extended range, there was literally nothing like the B-29 in the sky, With a Maximum takeoff weight more than twice that of the B-17 and an extra thousand miles of range, she was able to perform a task (massive carpet bombing of Japan) that the B-17 couldn't do.
It also just occurred to me that another reason for the fame of the B-17 is her reputation of “ruggedness”. While the plane was certainly well-built and performed some remarkable feats, the B-29 was never given the same chance. While bomber crews in Europe had to contend with swarms of Luftwaffe fighters and flak batteries, the B-29 entered service against a much-depleted Japanese fighter force. Fewer planes were able to limp back home to photogenic landings because they didn’t get as wounded to begin with.
Sources: To Command The Sky and A Time-Life History of WWII