Because it was designed for older hardware, version 1.5 has very low system requirements, which is why it remains popular for older PCs.
Since Adobe has retired this version, it is primarily available through community-driven archives: Internet Archive Descargar Adobe Audition 1.5 Gratis Free
If you still want the vintage experience, keep it offline, in a virtual machine, and never input personal passwords or banking on that system. Stay safe, and happy audio editing. Because it was designed for older hardware, version 1