Imagine you're a disciple of Christ. You seen Him on earth, you ate with Him and spent time with Him. People started to associate you with Jesus as Peter was associated with Him. Jesus dies and is then resurrected. He's then seen by over 500 others (1 Cor 15:6) before ascending to heaven. After Pentecost people start to preach the crucified Christ. The evidence for this story is that the people who preach this message lived their lives along side Jesus. Some of the Christians were eye witnesses to the risen Christ but despite this the Holy Spirit still chooses to accompany their preached word with signs and words to testify to the validity of that word (Acts 14:3). You would have thought that the accounts of 500 spectators would have been sufficient to convince the unbelieving world.
God goes further than us. Why should we stop seeking signs and wonders to accompany the preached word? We shouldn't. Paul was rich in theology and miracles. He understood the purpose of both. God sometimes uses signs and wonders to testify that we are preaching the real gospel. We must expect more.