Why are people hesitant to give a chance to a new political party?

I see a lot of pushback from older party supporters to any new politician/party. But isn't it how we develop as a state ? By instigating competition between the political parties so each of them have to perform and serve the people better than the other if they wanna come back to power again?

Right now the parties and politicians seem to be coasting without any external threat and we can take the power back in our hands this way.