Blue Beetle is part of a rather legendary run of Justice League International where Blue Beetle and Booster Gold had an amazing friendship. They got into all sorts of awesome trouble together. Outside of that, he has existed in one incarnation or another for decades, and has been dead for sometime ever since a rather pivotal event pre-New 52 and it really seemed like he was going to be one of those characters that would probably stay dead, not coming back during several events where they could have easily done so.
Also, for some people he is their Wally West, Stephanie Brown, or Cassandra Cain. Why does a certain segment of the fandom lose their collective shit over them? Same basic reason.