Why do we do this?

I have a serious question. 
Have you heard anyone beginning a testimony with anything like ‘Ever since I repented of my sin and believed in Christ. . .’?
I haven’t, not lately. They always begin with somethimg like:

‘Since I gave my heart to Jesus. . .’

‘Since I accepted Jesus. . .’

‘Since I received Christ. . .’

‘Since I chose Christ. . .’

Why is that?