Just a little over a decade ago, Sega had their own console, and was generally regarded as one of the major companies in this industry with a big booth at E3 every year. And as recently as last year they had major presence with Sonic Boom and Alien: Isolation.
Now they have announced that they won't have an E3 booth at all this year, mainly because of all the restructuring that was announced a few months back. Some Sega titles will be visible at Sega's partners, but will be scattered around the expo. Here is the official statement from Sega on the matter:
"Over the next months, SEGA of America will be focusing on the restructure and relocation to Southern California, and we have decided to not attend E3 with our own booth this year. With the majority of our bigger titles launching later in 2015/2016, particularly those from our AAA studios Relic Entertainment, Sports Interactive and Creative Assembly, we are concentrating our efforts for some of these major announcements after our relocation. Instead, we will be collaborating with our various business partners for this year's E3 show."
Thanks, Game Informer