Here's why:

* Nuclear Fusion: Stars generate energy through nuclear fusion, primarily fusing hydrogen into helium. The more massive a star, the more gravity it has, squeezing its core and creating higher temperatures and pressures.

* Faster Burning: These high temperatures and pressures lead to a much faster rate of fusion. Think of it like a bonfire – a larger fire burns hotter and consumes its fuel much faster.

* Short Lifespan: Since massive stars burn through their fuel very quickly, their lifespans are drastically shorter compared to smaller stars.

Here's a general rule of thumb:

* A star 10 times the mass of our Sun will only live for about 10 million years.

* Our Sun, a medium-sized star, is expected to live for about 10 billion years.

Note: The exact lifespan of a star is also influenced by other factors like its chemical composition and rotation rate.