Because a lot of people have died in at least two major World Wars to ensure that people have the right to vote if they choose. The very least we can do is take that right seriously, and that means having some idea what the various political parties stand for.
You don’t have to agree with them, you don’t have to get into debates with people over the policies, you just need to know what each candidate’s policies are and make an informed decision at the polling booth on who you would like your elected representative to be.
If you think the Labour candidate will retire a month after the election, then don’t vote for them. If you think the Greenie candidate is the bad kind of Tree-Hugging Communist, then don’t vote for them. If you think the Silly Party are a waste of space, don’t vote for them. But don’t get worked up over it, and don’t try and change anyone else’s opinions on “political” subjects. You can’t do it and it just creates arguments, hostility, and stress.