For good or bad, I suppose TMP uniforms would have to be changed as the movie sequels continued. As the cast aged and changed, I don't know how those TMP could have accomodated them.
Nothing against the cast or TMP uniforms. But it seems those beige PJs wouldn't have had a long run in the movies anyway.
If I remember correctly, one of the problems with the TMP uniforms is that the male cast couldn't sit down in them without risking injury.