Most irregular verbs exist as remnants of historical conjugation systems. What is today an exception actually followed a set, normal rule long ago. When that rule fell into disuse, some verbs kept the old conjugation. If you've ever noticed, verbs that are irregular tend to be the most commonly used ones. That said, one of the reasons could be the constant use of these verbs. Perhaps they started out as regular verbs, but gradually evolved and were modified into the forms we now know. Perhaps you think that "irregular " means something out of the ordinary, and in common parlance it does, but if you look up irregular in the dictionary, you'll see that the first definition is a little different. "Irregular" describes something that does not adhere to established rules.
Defining an Irregular Verb
Irregular verbs live by their own set of rules; they are the radicals of the English language. Most of the verbs in the English language are irregular verbs.
A regular verb, like "walk" looks like this:
Present Simple: I walk to gym every day.
Present Progressive: I am walking to gym today.
Past Simple: I walked to gym yesterday.
Present Perfect: I've walked to gym all week.
You've known the tenses since you were a child. In fact, when English-speaking children or English learners come across unfamiliar irregular verbs, they instinctively employ the form for a regular verb. For example, when a child hears "speak," without any prompting, he might say "speaked" when speaking about the past. When people hear it, they might think it's cute, but it should teach everyone interested in such things a valuable lesson about irregular verbs.
Learning Irregular Verbs
Since there are no specific rules regarding conjugating the tenses of irregular verbs, the only way to really learn them is to keep your ears open. Every time you learn a new verb, make sure you know all the conjugations of that verb so that when you use it you don't misspeak.
Here are a couple verbs that are commonly misspoken to get you started on your irregular adventure:
To Drink: I drink coffee every morning. I drank six cups of coffee yesterday. I have drunk 27 cups of coffee this week.
To Go: I go crazy when people kick my chair in movie theaters. I went crazy when I ran out of coffee. I have gone crazy four times this month.
To Swim: I swim in Lake Erie every summer. I swam through lots of garbage in July. I have swum through toxic sludge a few times.
To Have: I have a caffeine addiction. I had caffeine poisoning last month. I have had a caffeine addiction for seven years.
To Be: I am addicted to caffeine. I was tired until I found you, dear coffee! I have never been happier.
Impact of the Misuse of Irregular Verbs
The English language works, more or less, without paying too much attention to whether the speaker is using the verb correctly or not. When an English learner says, "yesterday I speaked with the President," it makes as much sense as if he'd said "spoke." That flexibility is why English remains the lingua franca; one does not have to speak it properly for it to be understood.
Benefit of use
If you want to sound intelligent or at least like a native speaker, you should mind your irregular verbs. They aren't hard to remember, and they really do make a difference when you're speaking with anyone, whose opinion you care about. Having a firm grasp on one's irregular verbs displays a command of the English language. Teachers, bosses, and English majors cringe when someone says "I should have drank" or "I should have went." Such sentences are understandable but just plain wrong. Correctly, they should be said "I should have drunk" or "I should have gone." Sometimes conjugations are nebulous or dependent on how English is spoken in that part of the world; but, most words have three forms, and it's good to get them right. The most common English verbs, like "go" or "have" or "be," are all irregular and take a bit of practice to master. When you have your irregular verbs down pat, you won't be able to help from noticing how many people have them all wrong. Getting them right shows a pride and responsibility that should be more common in English speakers.
English is the most versatile and expressive language on the planet, and its native speakers should put forth the effort to be a good example for the rest of the world, most of whom are spending a great deal of money and time learning it.