Allah, the Exalted, says:
“And your lord has commanded that you shall not worship (any) but Him and (show) goodness to your parents. If either or both of them reach old age with you, say not to them (so much as) 'Ah' nor chide them, but speak to them a generous word. And make yourself submissively gently to them with compassion, and say: O my Lord! Have compassion on them, as they brought me up (when I was) small.” Holy Qur'an (17:23-24)
If your friends give you a nice present, you will certainly thank them and your love will grow towards them.
If someone offers you help and assistance in your life, surely you will respect them and recognize their favour and kind attitude.
No one does more for you than your parents and it is they of all people who deserve great love, thanks, and respect. They are the ones who bear tiredness and difficulty for the sake of us, their children.
A mother first carries her child as an embryo (foetus) in her womb and it is fed by her blood. Then when she has given birth, she spends nights on attendance, taking care of and watching over her baby with love and affection.
Fathers also take part in caring and giving affection, and go to work and strive to provide food, shelter and other material necessities. In addition, both parents spend time educating their children and rearing them towards adulthood.
In the verses quoted above, Allah commands us to worship and obey none but Him. And at the same time He commands us to love our parents and acknowledge their favour and benevolence to us.
Allah also enjoins us not to speak unkindly or harm them, not to give even as much as a sigh against them, especially when they grow old or are in need, or unable to do things for themselves.