Baby weight ?

kay
I saw my midwife today and asked what she thought my baby would be weighing. She said she couldn't tell. It's just I've seen on here that many mums to be are being told. I'm in the UK. Any opinions on why so many mums to be are being told but mine couldn't? :( I'm 35 weeks and she said fundal height is measuring at 33 but not concerned as she said she is on the middle line 50th centile. Any advice would be greatful. Thanks