Why Cu+2 in activity series and not Cu+1?

Cu can form 2 cations: Cu⁺ and Cu²⁺.

Cu⁺ ion can only exist in solid state or in complexes, but cannot exist in aqueous solution. In aqueous solution, Cu⁺ ion undergoes disproportionation (self-redox reaction) to become Cu metal and Cu²⁺ ion.
2Cu⁺(aq) → Cu(s) + Cu²⁺(aq)

In other words, only Cu²⁺ ion exists in aqueous solution between the two ions of copper. The activity series is based on aqueous solutions, and thus only Cu²⁺(aq) ion appears in the activity series.

Because you're not looking at a very complete activity series, and that's probably because Cu{+} isn't as common as Cu{2+}.