Why, in the song "My Generation" by The Who, does the singer slur and stutter many of the words?

Pete Townshend once said he always tried to write toward the strengths of the individual members of the Who. To that end, he put the stutters in “My Generation” because both he and Roger Daltrey were “huge fans of John Lee Hooker and Johnny Cash, both of whom occasionally stuttered.” The BBC initially refused to play the song, fearing listeners would be offended, but as the song became a hit the broadcast company capitulated.

The song, composed by Pete Townshend at the age of twenty in 1965, was written for rebellious British youths called Mods, and expressed their feeling that older people "just don't get it".

Another salient aspect of "My Generation" is Daltrey's delivery: an angry and frustrated stutter. Various stories exist as to the reason for this distinct delivery.

One is that the song began as a slow "talking" blues number without the stutter (in the 1970s it was sometimes performed as such, but with the stutter, as "My Generation Blues"), but after being inspired by John Lee Hooker's "Stuttering Blues", Townshend reworked the song into its present form. Another reason is that it was suggested to Daltrey that he stutter to sound like a British mod on speed.

It is also proposed, albeit less frequently, that the stutter was introduced to give the group a framework for implying an expletive in the lyrics: "Why don't you all fff... fade away!" However, producer Shel Talmy insisted it was simply "one of those happy accidents" that he thought they should keep. Roger Daltrey has also commented that he had not rehearsed the song prior to the recording and he was unable to hear his own voice through the monitors. The stutter came about as he tried to fit the lyrics to the music as best he could, and the band decided it worked well enough to keep.

https://en.wikipedia.org/wiki/My_Generation_(The_Who_song)