Why are verbs different in Spanish?
I would like to know why the verbs change instead of staying the same.
Among the broad categorizations of languages, you will find the terms "analytic" and "synthetic" (other distinctions are possible). The Romance languages generally fall in the "synthetic" category" (which is to say that there are changes to the endings of words [they are inflected]) to indicate grammatical relationships.
At the other extreme, you have the analytic languages (mostly Asian) where nouns and verbs never change. If you wish to suggest plurality or some tense, you need to add a word(s).
English falls somewhere in between. Once it was more synthetic but the tendency is towards being more analytic. Most English speakers would not accept "I/you/he/she/ti/we/they be" as correct/standard but this sort of thing is quite common in "Black English"/"Ebonics".
Because they are conjugated to express person, tense, mood, aspect and voice.
Are you referring to all those funny changes such as "I am", "you" are", "he is", "I was", "you were" instead of the much simpler "*I/you/he be"?