Well the simple answer is that Allah and his Prophet (peace be upon him) said so. In Qassas Ul Qnbiya a lecture series delivered by Maulana Makki Al Hijazi, he talked about how Music and singing was introduced by Shaitaan to sway men and women from the paths of Allah. And how the various Prophets (peace be upon all of them) came and destroyed such instruments, practices and customs. In Holy Quran and Hadith it is mentioned very clearly and May Allah help me and you to walk on the straight path.
In Surah Luqmaan, Allah Taala states,
And from mankind are those that purchase futile speech in order to mislead others from the path of Allah. Under the commentary of this verse, ibn Abbaas [Radhiallaahu anhu] states, ‘futile speech’ refers to music and things related to it. (Durrul Manthoor vol.5 pg.307).
Nabi [Sallallaahu Alayhi Wasallam] mentions,
‘There will be people from my Ummah who will seek to make lawful fornication, wearing of silk, wine and the use of musical instruments.’ (Bukhaari vol.2 pg.837).
Rasulullah [Sallallaahu Alayhi Wasallam] states,
‘A group of my Ummah will drink wine calling it by other than its real name. merry will be made for them through the playing of musical instruments and by the singing of females. Allah will cleave the earth under them and turn them into apes and swines.’ (Abu Dawud vol.2 pg.519)
Rasulullah [Sallallaahu Alayhi Wasallam] further mentions,
‘Music grows hypocrisy in the heart just as water causes crops to grow.’ (Bayhaqi vol.10 pg.222).
The easiest way to bring Islam in our lives is to make constant dua to Allah to help us. InshaAllah if we would do the same for this explicit order of Allah and his Prophet (peace be upon him), InshaAllah it would become very easy for us.