It used to be prior to the opening of the Jubilee Line. When that line opened in 1977 the Stanmore branch (upon which West Hampstead resides) was split from the Bakerloo Line and became the northern end of the Jubilee Line. From Baker Street the Bakerloo Line only goes via Paddington and Queens Park to Harrow & Wealdstone.
Of course there are two other stations bearing the name of "West Hampstead" but we need not go there.