Generalisations to follow , but cover the majority ( but obviously not all ) of the circumstances .
Most single parents are women . Most have not chosen to raise a child / children on their own .Being a single parent is tough going , especially if you don’t have much / little support from the father / other family members .
It can be very lonely and unless you are in a decent job and can arrange good childcare it will be difficult for you to work / cover sickness especially when the kids are younger . When you have younger kids it is difficult/ expensive to organise baby sitting etc if you don’t have family nearby . You don’t have anyone on hand to share simple things like watching tv / having a glass of wine / moaning about your day etc .
It is hard from an emotional view point of having to make decisions on your own . So I think some ( although ) not all of single mums come from the starting point of feeling some degree of being vulnerable and alone . Again obviously not all , as some may be in a far better position after escaping an abusive relationship / value independence .
On the whole , life is easier if there are 2 adults / preferably parents to share the load .
This is without throwing into the equation those who may be even more vulnerable due to past relationships / other trauma .
I totally agree about what others have flagged up that there are sadly some men who will manipulate and seek out the more vulnerable single female parents for very sinister reasons . Even if it isn’t the worse possible motive , they may have other financial motives or just that they are happy to have someone else do all the work / housework etc .
I think the issue can be that when you meet someone you can be so caught up in the really exciting phase of falling in love . You are looking at them through rose tinted glasses , you may overlook obvious red flags , accept their version of previous relationship issues - the crazy ex etc . You want the relationship to work and are prepared to invest a lot in it . The new love may have a string of failed relationships behind them , but it will be different for you ….
It is always an issue when a new partner moves in really quickly when you are a single parent . You are still in the honeymoon phase and aren’t being objective and probably don’t know the person that well . Your child / children are very vulnerable then and sadly in a very few circumstances there can be very bad outcomes .
There will also be mums who will prioritise their relationship over their children . The mum’s new partner probably didn’t say - I hate kids and I want yours to leave as soon as possible . The new partner will have been manipulative in some cases or the mum simply would always prioritise a relationship over all else .
There are decent men out there ( not sure where ???) and many will make these relationships work . Waiting until your kids turn 18 ( if they are young ) is possibly overkill but taking things slowly with a new partner as a single parent and not rushing to move them in is the best thing you can do for your child .