- it is immensely capital intensive at scale. Your average excavator runs in the mid 5 digits, cranes and other specialized equipment way more. If you want to start a nationwide company, no one is stopping you, but be ready to shell out hundreds of millions of dollars before you made a single cent of income.
- Staffing is just as bad... you can't outsource the grunt work to the cheapest contractor overseas, you need actually certified people on site and most young people don't want to work in that area anymore as it is really hard, literally back breaking work.
- it is, and that for good reason, extremely regulated by government. No one dies if Facebook is down for an hour because someone fucked up a deployment. Mistakes in construction can cost lives or cause serious bodily harm or damages to nature (e.g. a sewer leaking into a groundwater table).
- almost none of it is automatable or in any way "disruptible" by a startup. Sure you can improve a bit by investing in automation or better digital tooling, but the ROI is in the single digits.
- most of the industry is decentralized small contractors. You can't go viral with construction, you can't build monopolies to extract rents later on.
- regulations are completely different everywhere on all levels, meaning you can't do a "build a standard whitelabel solution and sell it for cheap" job.
- most of the industry is extremely local and "knowing" people is how you get business. At the same time, purchasing is extremely local as well. If you want to construct a new home, you ask other home builders on recommendations for contractors.
- ETA: Yes of course there are giant companies in the construction world, but these companies don't do any small scale shit, these companies don't even return calls unless you're talking dozens of millions of euros of volume. But you can't really "disrupt" these either because of the sheer amount of everything you need just to get off the ground.
- ETA2: Another issue is a lot of the trades are run by older people with a ... seriously lacking understanding of modern IT. You'd be surprised how many essentially run off of Outlook, Excel and a CAD program. You'll have a very hard time pitching something to a crowd that has specialized in a specific thing and all but ossified there.
- Testing opportunities are scarce. Construction is an insanely risky business, delays causing significant followup costs and penalties, so you'll have it even harder to pitch something unevaluated to someone.