Irish citizens have the right to vote in European and Irish elections, including general elections, local elections, presidential elections and referendums. This right is not extended to all residents of Ireland. For example, non-EU citizens can only vote in local elections.
By obtaining Irish citizenship, you acquire the full complement of voting rights. This gives you the chance to exercise your democratic rights, and to have a say as to how the country is run. This will be important if you have made (or intend to make) Ireland your home.