One reason I think there are strong feelings with the VP selection

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17. The following VPs have become President since 1900

Teddy Roosevelt (McKinley assassinated)
Calvin Coolidge (Harding died in office)
Harry Truman (FDR died in office)
Lyndon Johnson (Kennedy died in office)
Richard Nixon (ran in 68 after serving as VP from 53 to 61)
Gerald Ford (Nixon resigned)
George HW Bush (ran in 88 while serving as VP from 81 to 89)
Joe Biden (ran in 20 after serving as VP from 09 to 17)

In addition the following were nominees but lost
Richard Nixon (ran in 60 while serving as VP from 53 to 61)
Hubert Humphrey (ran in 68 while serving as VP from 65 to 69)
Walter Mondale (ran in 84 after serving as VP from 77 to 81)
Al Gore (ran in 00 while serving as VP from 93 to 01)
Kamala Harris (running now while serving from 21 to 25)

There have been 25 VP in that time frame. That is about a 1/3 chance of becoming President (slightly less if Harris loses, slightly more if Harris wins) and a nearly 1/2 chance of becoming a nominee. It is quite reasonable to think a VP has a pretty decent chance of becoming President someday and very reasonable to think they will become a nominee someday.