Bit of a nitpick, but ELF binaries are not used "only in Linux". OS X (Mach) and Windows (PE) are really quite exceptional here.
System V R4, HP-UX, NetBSD, Linux, Solaris, AIX, IRIX, FreeBSD, OpenBSD, DragonFly BSD, OpenVMS, QNX, Syllable, MINIX, BeOS/Haiku, RISC OS, GP2X, Dreamcast, Gamecube, PSX, PS2, PS3 (maybe NetBSD or FreeBSD ish), PS4(based on FreeBSD), AmigaOS 4, Morph OS, AROS, Open Firmware, and probably a whole bunch of other systems use ELF binaries.
System V R4, HP-UX, NetBSD, Linux, Solaris, AIX, IRIX, FreeBSD, OpenBSD, DragonFly BSD, OpenVMS, QNX, Syllable, MINIX, BeOS/Haiku, RISC OS, GP2X, Dreamcast, Gamecube, PSX, PS2, PS3 (maybe NetBSD or FreeBSD ish), PS4(based on FreeBSD), AmigaOS 4, Morph OS, AROS, Open Firmware, and probably a whole bunch of other systems use ELF binaries.