At one time interphase was referred to as the resting phase of the cell cycle why do you think the description is no longer used?

During interphase there is much metabolic activity.

Some examples of processes that take place in interphase are: transcription and translation; DNA replication (which occurs at mid-interphase); glycolysis in the cytoplasm; aerobic respiratory reactions in mitochondria; both light-dependent and light-independent reactions of photosynthesis in chloroplasts; digestion in lysosomes; lipid synthesis in the smooth endoplasmic reticulum; protein processing and modification in the Golgi body.

So it's not too restful between divisions!