Assalaamu alaykum. The legislations of Islam have many worldly benefits, and the Islamic lifestyle also protects us from much harm. If one follows the Islamic legislations predominantly to achieve these worldly benefits of Islam, does that go against sincerity?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

Following the teachings of Islam leads to happiness in the religion and the worldly life; all the matters will be as they should be, and one achieves every goodness and repels every evil. So if a person is committed to the teachings of Islam with sincerity to Allah and in order to achieve these great benefits that Allah urged us to achieve, then this does not contradict his sincerity to Allah. 

The Prophet urged us to do many acts of worship because of the benefits that they have, as in the authentic hadeeth of Anas, may Allah be pleased with him, who narrated that the Prophet said, “The one who desires ample provisions and that his life be prolonged should maintain good ties with his blood relations”. [Al-Bukhaari and Muslim]

There are many ahaadeeth like this.

Indeed, Nooh (Noah), may Allah exalt his mention, said to his people: {Ask forgiveness of your Lord. Indeed, He is ever a Perpetual Forgiver. He will send [rain from] the sky upon you in [continuing] showers and give you increase in wealth and children and provide for you gardens and provide for you rivers.} [Quran 71:10-12]

Al-Ashqar said in Maqaasid Al-Mukallafeen:

“Intending such benefits is among the acts of worship that are intended for Allah, the Law Maker, and which are required from the Mukallaf (the person who is competent for religious assignments), because it suits his situation. If he acts according to this, then his affairs will be rectified and his worldly life and his Hereafter will be protected for him. It is better if we clearly determine here that aspiring for the fruits of the acts of worship – whether they are pure acts of worship or customs that are considered as acts of worship [such as keeping ties with kinship, for example] – does not contradict sincerity as long as we intend to fulfill the objectives of the Law Maker [i.e. Allah] that result from such actions.”

Allah knows best.