Please, tell us about those "spots." But, YES, I understand your tone of frustration. Pulling purslane out of the soybeans the other day was an indication how they can stifle especially our plants that are direct sown into the garden. Transplanted, our garden team-mates have a better start but anytime another plant is gathering soil moisture and plant food from the root zone of our plant partners, our buddies will likely suffer.
Here, that weed has followed us from one garden to another. There had been no gardening on several of the pieces of ground where I've begun to grow things in years past. In one place, it had been a hay field. I don't remember seeing purslane in any of these places before I showed up with my plant compatriots.
I've talked before about how I have unintentionally created a garden path of Kentucky blue grass by walking across lawns into the gardens. The seeds are coming in on my shoes off a lawn that is mowed. It's likely that this shoe-hitchhiking also occurs with purslane. BTW. I also see purslane here in lawngrass. It looks to have a very tough time but still flowers and must set seeds. I suspect that they wouldn't be there if someone was not caring for our lawn comrades.
If we were talking about portulaca as a group, they just about HAVE taken over the world. Perhaps we should accept the common garden portulaca as a garden bedfellow.
drier spots, hard packed mostly clay, soil that gets no watering at all other than the rains, but purselane will grow in such spots here. the tiny seeds must get splashed or moved around somehow. we've had maybe two inches of rain the past six or more weeks.
we don't have purselane in the lawn, i've also managed to get it mostly out of a few gardens but a few seeds will sprout of it in those. if i'm good at keeping it from flowering and dropping more seeds it is under control for those. the worst gardens are those that i newly turn over. i suspect the seeds survive for a long time in the soil and one plant can drop hundreds of thousands of seeds. this year i have done a good job of getting them all before they drop fresh seeds.
the more decorative moss roses we've planted here at times through the years but they do not persist and even if i let those go to seeds they don't come back enough. i used to know someone who had a nice patch of them in a more shady spot and they would come back for her each year to fill that area back in but you did have to weed them to give them a chance.