For 2 reasons.

[1] I only did broadcast/scattershot approach for the first year. After I got kicked off benefits the 2nd time (for attending a meeting of my startup -- an unpaid position -- in another part of the country) I stopped trying for anything I could do at all, anywhere, and started targeting my applications far more specifically, at things I was a really good fit for, with customised CVs etc.

No difference. Maybe a slightly higher rate of rejection letters.

[2] As others have said, timing.

I was freelance for most of the period 1996-2001 and 2003-2007. I decided to return to F/T work in '07 and applied for about 500 positions in 4 months before I got my first interview. I was hired over the phone, first interview.

It's getting to the interview that's hard. I interview well. I'm smart, lucid, eloquent, approachable.

These days, that means keyword matching, to get past 1st and maybe 2nd level selection.

2009/2010 were very bad. 2011, I got a role, but only very very briefly. 2012, I was even flown to Scotland for a 2nd interview, then got a second, non-IT role. 2013, I retrained in TEFL and went looking for teaching roles. End 2013, I applied for, and in early 2014, I got, a role in Brno, Czechia.