Reasoning is we dominate so much and want to get more money in. Yeah if we get all in we're likely against a set, but there are a fair few combo draws we'd love to get it in against, J9 J8 89 86 96 64 of clubs, we're v happy to get more money in against Ax of clubs and this is our best chance do that while we're still ahead, and we're not in terrible shape if we are up against AT, an overpair, 2 pair or a set, some of which we probably get to fold. I guess you're saying the main downside is that we're not in great shape when we get it in, but I don't think it's as bad as you think, see stoves below. The other possible downside is that we perhaps lose a bet from worse top pair hands, but I don't think they're all that likely to be in villain's range and if they are they're unlikely to bet again, or that we get worse flush draws to fold when they would have hit, but I think the risk of that happening is outweighed by the extra money we make from the times they call and miss.
Board:

Dead:
equity win tie pots won pots tied
Hand 0: 46.235% 46.24% 00.00% 5035 0.00 { KcTc }
Hand 1: 53.765% 53.76% 00.00% 5855 0.00 { TT, 77, 55, Jc9c, Jc8c, 9c8c, 8c6c } - vs sets and good combo draws (overcard+gutshot fd or up and down fd)
equity win tie pots won pots tied
Hand 0: 42.548% 42.48% 00.07% 9252 15.00 { KcTc }
Hand 1: 57.452% 57.38% 00.07% 12498 15.00 { TT, 77, 55, T7s, 75s, T7o, 75o } - vs sets and two pairs
equity win tie pots won pots tied
Hand 0: 47.976% 47.93% 00.05% 14234 15.00 { KcTc }
Hand 1: 52.024% 51.97% 00.05% 15436 15.00 { TT, 77, 55, AcQc, AcJc, Ac5c, Ac4c, Ac3c, Ac2c, Jc9c, T7s, 9c8c, 8c6c, 75s, T7o, 75o } vs sets, two pairs, good combo draws and some nut fds