Not a very compelling reason. There are lots of other arenas with challenging material. This is true, but you may not be able to appreciate it yet. Imagine for a moment how von Leewuenhoek and other early microscopists must have felt when they first were able to examine the world of living cells. This is a unique view of life and its processes.
Cells are microcosms of larger living systems.
Each single cell is capable of all of the functions of life, and must meet all of the same needs of larger multicellular organisms. Cells are relatively easy to manipulate and test in the laboratory. The simplicity, small size, and simple requirements of cells make them ideal experimental subjects. Many processes, including regulation of metabolism and control of the utilization of genetic information, are most easily studied in the laboratory with cell systems. This is where modern biology 'is at'.