I don't think that's a direct comparison. gov.uk looks closer to something like https://www.usa.gov/, which is similarly functional. The Whitehouse website is more political and maybe would be closer to to Downing Street's page https://www.gov.uk/government/organisations/prime-ministers-... which has more photos.

I agree that might be a fairer comparison however I would argue is just as a accessible as https://gov.uk/ (to be expected since it's the same site), I don't think the addition of images makes it less so.