Well, I can only speak for myself and not for others, but when my kids were younger I deliberately chose to be single and raised them, even if it was only a weekend out of two, so that they got stability out of it. I've been single 14 years. Their mother at the time had had a few failed relationships straight and I felt, (wether it was justified or not isn't relevant, I just felt that way) that it was a good idea to offer them on at least one side a stable environment they felt safe in. They got used to having dad all to themselves and, I hope, it made them feel more stable and valued as a consequence.
As for loneliness, well, when I'm with my girls, there's no such thing; I often say I don't feel like a regular normalguy UNLESS I'm with my daughters lol.As for when they werent there, I replaced someone's presence with activites, or friends, or family to alleviate. It's helped to make me realise I don't NEED to have someone in my life necessarily to grow as a human being, that if I so chose to find companionship, it's because I want it, not need it. Recently I started talking to someone and while I'm kind of proceeding gingerly because it's been so long and I'm...not quite sure what I'm doing lol,it allows me to take my time because I don't feel the need for urgency or pressure. And I'm so used to not feeling pressure, or give pressureto someone else now, that it helps create an environment that's rather secure, condusive to honesty and trust, which I like very much.
Of course, that's my situation under some very specific circumstances. I wouldn't presume to know if the same can apply to everyone else, all our lives are so very different. But, in short, to me, the effort went to raising the girls correctly first and foremost, so now, at the age of 42, I can concentrate on a different aspect of my life without distractions or not really knowing wether I was pursuing something that I really wanted or because I felt I absolutely needed to, at all cost. In essence, now that I know how to live with myself, I can try to live with others...
I hope this helps solve your questionings