Why do guys do this ?

Ok so whenver I go somewhere and I'm the only girl , guys alwaays say get some when I walk up . And they even do that when I'm with my frends . Guys also tell me I have a nice asss and nice booobs . And I always feel awkward . Like thanks ? But I mean , come onn ? I'm only 13 and guys who are like 10-18 years old are saying it to meeh . Why do they do this ? And am I the only one that feels awkward !?