Because there is no other way for us to interact with our environment? If we do not trust our senses, we would be too afraid to walk, open our eyes, eat/drink, etc...
This is a generally good answer indeed (at least according to me) and it is similar in form to the one Hume gives (we have to live in this world) - although there have been many philosophical attempts to answer "Hum's Problem of Induction" since then.
It cannot be considered a logically
good answer, though, because it is:
- Appeal to consequences - We must trust our senses because not doing so leads to undesirable consequences (fear of walking, fear of opening eyes, fear of eating/drinking, not interacting with environment)
- Begging the question - One must assume the conclusion (our senses are trustworthy) is true to determine the premise is valid (that there exists an environment to interact with; that we can walk, open our eyes, eat/drink)